6502-ACE

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. Start with Your ACE, the tour of this board.

Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The ACE (All-in-one Computer Experience) is a complete, self-contained 65C02 computer on a single PCB. It integrates everything found across the COB's modular cards — CPU, memory, video, audio, storage, serial, GPIO, RTC, and keyboard controller — onto one board, delivering the full experience without a backplane or expansion cards.

Architecture

All AC6502 computers share:

CPU: 65C02 (or accurate emulation)
Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer (YOU ARE HERE)
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into `.prg` images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the ACE board.

ACE Board

Hardware/ACE Board/

The single integrated board hosting the W65C02S CPU and all peripherals. Provides:

CPU: W65C02S running at 1 or 2 MHz (jumper-selectable)
RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
ROM: 32KB EEPROM (28C256)
Video: Pico9918 (VGA 640×480)
Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
Storage: Storage adapter socket
Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
GPIO: 65C22 VIA (20 GPIO pins, 2× 16-bit timers, shift register)
RTC: DS1511Y real-time clock with battery-backed NVRAM
Keyboard Controller: ATmega1284P running AB Controller firmware
Input: PS/2 keyboard connector and 8×8 keyboard matrix header
Joystick: Two Atari 2600-compatible joystick ports (J6 JOYSTICK A on VIA PORT A, J8 JOYSTICK B on VIA PORT B), read as JOY(2) and JOY(1) respectively
Clock: 16 MHz DIP-14 full can oscillator (X1); drives the ATmega1284 at 16 MHz and the 65C02 at 1 or 2 MHz via the 74HC163 divider (J1 PHI2 SELECT jumper)
Reset: Manual reset button (SW17, just above Esc) connected to the ATmega1284, which also provides power-on reset to the 65C02
Power: 5V DC via barrel jack

Revision History

Rev 1.1

Fixes the gating of the LOADL and LOADH latch-enable signals for the 74HC573 latches (U21, U22) that drive the AS6C4008 banked SRAM. In Rev 1.0 the final two decode gates (U13C/U13D) were NANDs, which left the latches pulsing while idle and allowed spurious loads on reads, so the latches never reliably held a bank value.
The fix replaces the final NAND stage with a NOR function: LOADL = NOR(SEL_L, WB) and LOADH = NOR(SEH_L, WB), holding each latch enable low out of window and only pulsing on an in-window write. This makes banked RAM work correctly with no firmware change.
Implemented by adding one 74HC02 quad NOR (U23). The existing select logic in U13A/U13B is unchanged.
Some pull-up resistors changed from 1kΩ to 10kΩ: R1–R4 and R25 are now 10kΩ.
Added C31 (10µF electrolytic) at the power input for bulk decoupling capacitance.

Rev 1.0

Initial release.

ACE CF Adapter

Hardware/ACE CF Adapter/

A CompactFlash adapter board that connects to the Storage header on the ACE Board. Provides:

Interface: 8-bit IDE (True IDE) mode
Storage: CompactFlash socket. The BIOS filesystem divides the card into 256 disk banks of 1 MB each, so 256 MB is the usable capacity regardless of the card fitted

ACE RAM Patch

Hardware/ACE RAM Patch/

A piggyback patch board for Rev 1.0 of the ACE Board that corrects the extended RAM (banked SRAM) issue. Installs by plugging into the U13 (74HC00) socket on the main board. Provides:

Fix: Replaces the Rev 1.0 NAND-based latch-enable logic with a NOR function (LOADL = NOR(SEL_L, WB), LOADH = NOR(SEH_L, WB)), preventing spurious latch pulses and making banked RAM work correctly with no firmware change
Interface: DIP-14 piggyback connector into U13 on the Rev 1.0 ACE Board

Firmware

This repository contains PlatformIO-based firmware for the ACE board.

AB Controller

Firmware/AB Controller/

Firmware for the ATmega1284P keyboard controller on the ACE board. Provides:

Dual keyboard input: PS/2 and 8×8 matrix keyboard simultaneously
PS/2 scancode to ASCII conversion
Matrix keyboard scanning with hardware debouncing
Modifier key support: Shift (symbols/punctuation) and Ctrl (control codes)
Buffered output via 65C22 VIA with CA1/CB1 data-ready strobes
Independent enable/disable for PS/2 and matrix inputs, releasing PORT A / PORT B so the 6502 can read the joysticks that share them
6502 reset control: drives RESB on PC7, holding the CPU in reset for ~250 ms at power-on, and debounces the reset button on PC0
Optional jiffy clock: pulses NMIB from the DS1511Y SQW input; compiled out unless ENABLE_SQW is defined

See Firmware/AB Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure bases and laser-cut top panels for the ACE system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for the ACE board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

ACE Board

Reference	Qty	Value	Description	DigiKey	Mouser	Other
BT1	1	CR2032	Battery Holder	BAT-HLD-001-THM-ND	712-BAT-HLD-001-THM
C1, C9–C30	23	100nF	Disc Capacitor	478-5732-ND		AMAZON
C2, C3, C5, C6, C8	5	1µF	Disc Capacitor	478-7667-ND		AMAZON
C4, C7	2	2.2nF	Disc Capacitor	478-SR151C222KAATR1CT-ND		AMAZON
C31	1	10uF	Electrolytic Capacitor 16v	P966-ND		AMAZON
D1	1	LED	3.0mm Power LED	732-5008-ND		AMAZON
D2, D3	2	BAT85	Schottky Diode	BAT85SCT-ND	78-BAT85S	AMAZON
J1	1	PHI2 SELECT	Pin Header 1×3 2.54mm			AMAZON
J2	1	CTS EN	Pin Header 1×3 2.54mm			AMAZON
J3	1	RESET SW	Pin Header 1×2 2.54mm			AMAZON
J4	1	DCD EN	Pin Header 1×3 2.54mm			AMAZON
J5	1	VDD	Pin Header 1×2 2.54mm			AMAZON
J6	1	JOYSTICK A	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J7	1	PADDLES	Pin Header 1×4 2.54mm			AMAZON
J8	1	JOYSTICK B	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J9	1	PORT B	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J10	1	PORT A	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J11	1	AUDIO L	RCA Jack	PJRAN1X1U02X-ND	502-PJRAN1X1U02X
J12	1	DB9 MALE (DTE)	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J13	1	PS/2	6-pin Mini-DIN		806-KMDGX-6S-BS	AMAZON
J14	1	KEYBOARD	Pin Header 1×16 2.00mm			AMAZON
J15	1	AUDIO R	RCA Jack	PJRAN1X1U03X-ND	502-PJRAN1X1U03X
J16	1	AUDIO	Pin Header 1×2 2.54mm			AMAZON
J17	1	5V DC	DC Barrel Jack	2073-DCJ200-10-A-K1-K-ND	640-DCJ200-10-A-K1-K
J18	1	CART	Card Edge 2×20 2.54mm	A31723-ND	571-5-5530843-4
J19	1	BUS	Box Header 2×20 2.54mm			AMAZON
J20	1	VCC	Pin Header 1×2 2.54mm			AMAZON
J21	1	POWER LED	Pin Header 1×2 2.54mm			AMAZON
J22	1	STORAGE	Pin Socket 2×10 2.54mm Horiz	S5563-ND
R1–R4, R25	5	10kΩ	1/8W Resistor	RNF18FTD10K0CT-ND		AMAZON
R5–R23, R26–R34	28	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND		AMAZON
R24	1	330Ω	1/8W Resistor			AMAZON
SW1–SW13, SW15, SW18–SW29, SW31, SW33–SW41, SW43, SW44, SW46–SW49, SW51–SW58, SW61, SW64–SW66	54	Various	Cherry MX Switch 1.00u	CH196-ND		AMAZON
SW59, SW60, SW63, SW67, SW68	5	CTRL / ALT / FN	Cherry MX Switch 1.25u	CH196-ND		AMAZON
SW16, SW30	2	TAB / Backslash	Cherry MX Switch 1.50u	CH196-ND		AMAZON
SW32	1	CAPS LOCK	Cherry MX Switch 1.75u	CH196-ND		AMAZON
SW14	1	BACKSPACE	Cherry MX Switch 2.00u	CH196-ND		AMAZON
SW42, SW45, SW50	3	SHIFT / ENTER	Cherry MX Switch 2.25u	CH196-ND		AMAZON
SW62	1	SPACE	Cherry MX Switch 6.25u	CH196-ND		AMAZON
SW17	1	RESET	Tact Push Button 6mm			AMAZON
SW69	1	POWER	SPDT Switch	EG4326-ND	612-400MSP1R6BLKM6QE
SW70	1	IO ENABLE	8× DIP Switch SPST			AMAZON
U1	1	W65C02S	65C02 CPU		955-W65C02S6TPG-14
U2	1	W65C22	65C22 VIA		955-W65C22N6TPG-14
U3	1	Pico9918A	VDP (VGA)			TINDIE
U4	1	65C51	ACIA			JAMECO
U5	1	74HC163	4-bit Counter	296-8246-5-ND	595-SN74HC163N
U6	1	ATmega1284-P	Keyboard Controller MCU	ATMEGA1284-PU-ND	556-ATMEGA1284-PU
U7	1	AS6C62256	32KB SRAM	1450-1033-ND	913-AS6C62256-55PCN
U8	1	AT28C256	32KB EEPROM	AT28C256-15PU-ND	556-AT28C25615PU
U9	1	6581	SID Chip			LINK
U10	1	MAX238xNG+	RS-232 Transceiver	MAX238CNG+-ND	700-MAX238CNG
U11–U14, U16	5	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U15	1	AS6C4008	512KB SRAM	1450-1027-ND	913-AS6C4008-55PCN
U17	1	74HC30	8-input NAND	296-9196-5-ND	595-CD74HC30E
U18	1	DS1511Y	RTC + NVRAM	DS1511Y+-ND	700-DS1511Y
U19, U20	2	74HC138	3-to-8 Decoder	296-1575-5-ND	595-SN74HC138N
U21, U22	2	74HC573	Octal Latch	296-12815-5-ND	595-CD74HC573EE4
U23	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N
X1	1	16MHz	DIP-14 Oscillator	X947-ND	815-ACO-16-EK
Y1	1	1.8432MHz	Crystal	3155-1.8432M20P2/49U-ND	815-AB-1.8432-B2

ACE CF Adapter

Reference	Qty	Value	Description	DigiKey	Other
D1	1	ACT LED	3.0mm LED	732-5008-ND	AMAZON
J1	1	STORAGE	Pin Header 2×10 2.54mm Horiz		AMAZON
J2	1	Compact Flash	CF Socket	4827-101D-TAAB-R01-ND
R1–R4	4	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND	AMAZON
R5	1	330Ω	1/8W Resistor		AMAZON

ACE RAM Patch

Reference	Qty	Value	Description	DigiKey	Mouser
J1	1	74HC00 (U13)	DIP-14 Piggyback Socket
U1	1	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U2	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License.

6502-ACE

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. Start with Your ACE, the tour of this board.

Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The ACE (All-in-one Computer Experience) is a complete, self-contained 65C02 computer on a single PCB. It integrates everything found across the COB's modular cards — CPU, memory, video, audio, storage, serial, GPIO, RTC, and keyboard controller — onto one board, delivering the full experience without a backplane or expansion cards.

Architecture

All AC6502 computers share:

CPU: 65C02 (or accurate emulation)
Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer (YOU ARE HERE)
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into `.prg` images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the ACE board.

ACE Board

Hardware/ACE Board/

The single integrated board hosting the W65C02S CPU and all peripherals. Provides:

CPU: W65C02S running at 1 or 2 MHz (jumper-selectable)
RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
ROM: 32KB EEPROM (28C256)
Video: Pico9918 (VGA 640×480)
Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
Storage: Storage adapter socket
Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
GPIO: 65C22 VIA (20 GPIO pins, 2× 16-bit timers, shift register)
RTC: DS1511Y real-time clock with battery-backed NVRAM
Keyboard Controller: ATmega1284P running AB Controller firmware
Input: PS/2 keyboard connector and 8×8 keyboard matrix header
Joystick: Two Atari 2600-compatible joystick ports (J6 JOYSTICK A on VIA PORT A, J8 JOYSTICK B on VIA PORT B), read as JOY(2) and JOY(1) respectively
Clock: 16 MHz DIP-14 full can oscillator (X1); drives the ATmega1284 at 16 MHz and the 65C02 at 1 or 2 MHz via the 74HC163 divider (J1 PHI2 SELECT jumper)
Reset: Manual reset button (SW17, just above Esc) connected to the ATmega1284, which also provides power-on reset to the 65C02
Power: 5V DC via barrel jack

Revision History

Rev 1.1

Fixes the gating of the LOADL and LOADH latch-enable signals for the 74HC573 latches (U21, U22) that drive the AS6C4008 banked SRAM. In Rev 1.0 the final two decode gates (U13C/U13D) were NANDs, which left the latches pulsing while idle and allowed spurious loads on reads, so the latches never reliably held a bank value.
The fix replaces the final NAND stage with a NOR function: LOADL = NOR(SEL_L, WB) and LOADH = NOR(SEH_L, WB), holding each latch enable low out of window and only pulsing on an in-window write. This makes banked RAM work correctly with no firmware change.
Implemented by adding one 74HC02 quad NOR (U23). The existing select logic in U13A/U13B is unchanged.
Some pull-up resistors changed from 1kΩ to 10kΩ: R1–R4 and R25 are now 10kΩ.
Added C31 (10µF electrolytic) at the power input for bulk decoupling capacitance.

Rev 1.0

Initial release.

ACE CF Adapter

Hardware/ACE CF Adapter/

A CompactFlash adapter board that connects to the Storage header on the ACE Board. Provides:

Interface: 8-bit IDE (True IDE) mode
Storage: CompactFlash socket. The BIOS filesystem divides the card into 256 disk banks of 1 MB each, so 256 MB is the usable capacity regardless of the card fitted

ACE RAM Patch

Hardware/ACE RAM Patch/

A piggyback patch board for Rev 1.0 of the ACE Board that corrects the extended RAM (banked SRAM) issue. Installs by plugging into the U13 (74HC00) socket on the main board. Provides:

Fix: Replaces the Rev 1.0 NAND-based latch-enable logic with a NOR function (LOADL = NOR(SEL_L, WB), LOADH = NOR(SEH_L, WB)), preventing spurious latch pulses and making banked RAM work correctly with no firmware change
Interface: DIP-14 piggyback connector into U13 on the Rev 1.0 ACE Board

Firmware

This repository contains PlatformIO-based firmware for the ACE board.

AB Controller

Firmware/AB Controller/

Firmware for the ATmega1284P keyboard controller on the ACE board. Provides:

Dual keyboard input: PS/2 and 8×8 matrix keyboard simultaneously
PS/2 scancode to ASCII conversion
Matrix keyboard scanning with hardware debouncing
Modifier key support: Shift (symbols/punctuation) and Ctrl (control codes)
Buffered output via 65C22 VIA with CA1/CB1 data-ready strobes
Independent enable/disable for PS/2 and matrix inputs, releasing PORT A / PORT B so the 6502 can read the joysticks that share them
6502 reset control: drives RESB on PC7, holding the CPU in reset for ~250 ms at power-on, and debounces the reset button on PC0
Optional jiffy clock: pulses NMIB from the DS1511Y SQW input; compiled out unless ENABLE_SQW is defined

See Firmware/AB Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure bases and laser-cut top panels for the ACE system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for the ACE board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

ACE Board

Reference	Qty	Value	Description	DigiKey	Mouser	Other
BT1	1	CR2032	Battery Holder	BAT-HLD-001-THM-ND	712-BAT-HLD-001-THM
C1, C9–C30	23	100nF	Disc Capacitor	478-5732-ND		AMAZON
C2, C3, C5, C6, C8	5	1µF	Disc Capacitor	478-7667-ND		AMAZON
C4, C7	2	2.2nF	Disc Capacitor	478-SR151C222KAATR1CT-ND		AMAZON
C31	1	10uF	Electrolytic Capacitor 16v	P966-ND		AMAZON
D1	1	LED	3.0mm Power LED	732-5008-ND		AMAZON
D2, D3	2	BAT85	Schottky Diode	BAT85SCT-ND	78-BAT85S	AMAZON
J1	1	PHI2 SELECT	Pin Header 1×3 2.54mm			AMAZON
J2	1	CTS EN	Pin Header 1×3 2.54mm			AMAZON
J3	1	RESET SW	Pin Header 1×2 2.54mm			AMAZON
J4	1	DCD EN	Pin Header 1×3 2.54mm			AMAZON
J5	1	VDD	Pin Header 1×2 2.54mm			AMAZON
J6	1	JOYSTICK A	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J7	1	PADDLES	Pin Header 1×4 2.54mm			AMAZON
J8	1	JOYSTICK B	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J9	1	PORT B	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J10	1	PORT A	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J11	1	AUDIO L	RCA Jack	PJRAN1X1U02X-ND	502-PJRAN1X1U02X
J12	1	DB9 MALE (DTE)	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J13	1	PS/2	6-pin Mini-DIN		806-KMDGX-6S-BS	AMAZON
J14	1	KEYBOARD	Pin Header 1×16 2.00mm			AMAZON
J15	1	AUDIO R	RCA Jack	PJRAN1X1U03X-ND	502-PJRAN1X1U03X
J16	1	AUDIO	Pin Header 1×2 2.54mm			AMAZON
J17	1	5V DC	DC Barrel Jack	2073-DCJ200-10-A-K1-K-ND	640-DCJ200-10-A-K1-K
J18	1	CART	Card Edge 2×20 2.54mm	A31723-ND	571-5-5530843-4
J19	1	BUS	Box Header 2×20 2.54mm			AMAZON
J20	1	VCC	Pin Header 1×2 2.54mm			AMAZON
J21	1	POWER LED	Pin Header 1×2 2.54mm			AMAZON
J22	1	STORAGE	Pin Socket 2×10 2.54mm Horiz	S5563-ND
R1–R4, R25	5	10kΩ	1/8W Resistor	RNF18FTD10K0CT-ND		AMAZON
R5–R23, R26–R34	28	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND		AMAZON
R24	1	330Ω	1/8W Resistor			AMAZON
SW1–SW13, SW15, SW18–SW29, SW31, SW33–SW41, SW43, SW44, SW46–SW49, SW51–SW58, SW61, SW64–SW66	54	Various	Cherry MX Switch 1.00u	CH196-ND		AMAZON
SW59, SW60, SW63, SW67, SW68	5	CTRL / ALT / FN	Cherry MX Switch 1.25u	CH196-ND		AMAZON
SW16, SW30	2	TAB / Backslash	Cherry MX Switch 1.50u	CH196-ND		AMAZON
SW32	1	CAPS LOCK	Cherry MX Switch 1.75u	CH196-ND		AMAZON
SW14	1	BACKSPACE	Cherry MX Switch 2.00u	CH196-ND		AMAZON
SW42, SW45, SW50	3	SHIFT / ENTER	Cherry MX Switch 2.25u	CH196-ND		AMAZON
SW62	1	SPACE	Cherry MX Switch 6.25u	CH196-ND		AMAZON
SW17	1	RESET	Tact Push Button 6mm			AMAZON
SW69	1	POWER	SPDT Switch	EG4326-ND	612-400MSP1R6BLKM6QE
SW70	1	IO ENABLE	8× DIP Switch SPST			AMAZON
U1	1	W65C02S	65C02 CPU		955-W65C02S6TPG-14
U2	1	W65C22	65C22 VIA		955-W65C22N6TPG-14
U3	1	Pico9918A	VDP (VGA)			TINDIE
U4	1	65C51	ACIA			JAMECO
U5	1	74HC163	4-bit Counter	296-8246-5-ND	595-SN74HC163N
U6	1	ATmega1284-P	Keyboard Controller MCU	ATMEGA1284-PU-ND	556-ATMEGA1284-PU
U7	1	AS6C62256	32KB SRAM	1450-1033-ND	913-AS6C62256-55PCN
U8	1	AT28C256	32KB EEPROM	AT28C256-15PU-ND	556-AT28C25615PU
U9	1	6581	SID Chip			LINK
U10	1	MAX238xNG+	RS-232 Transceiver	MAX238CNG+-ND	700-MAX238CNG
U11–U14, U16	5	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U15	1	AS6C4008	512KB SRAM	1450-1027-ND	913-AS6C4008-55PCN
U17	1	74HC30	8-input NAND	296-9196-5-ND	595-CD74HC30E
U18	1	DS1511Y	RTC + NVRAM	DS1511Y+-ND	700-DS1511Y
U19, U20	2	74HC138	3-to-8 Decoder	296-1575-5-ND	595-SN74HC138N
U21, U22	2	74HC573	Octal Latch	296-12815-5-ND	595-CD74HC573EE4
U23	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N
X1	1	16MHz	DIP-14 Oscillator	X947-ND	815-ACO-16-EK
Y1	1	1.8432MHz	Crystal	3155-1.8432M20P2/49U-ND	815-AB-1.8432-B2

ACE CF Adapter

Reference	Qty	Value	Description	DigiKey	Other
D1	1	ACT LED	3.0mm LED	732-5008-ND	AMAZON
J1	1	STORAGE	Pin Header 2×10 2.54mm Horiz		AMAZON
J2	1	Compact Flash	CF Socket	4827-101D-TAAB-R01-ND
R1–R4	4	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND	AMAZON
R5	1	330Ω	1/8W Resistor		AMAZON

ACE RAM Patch

Reference	Qty	Value	Description	DigiKey	Mouser
J1	1	74HC00 (U13)	DIP-14 Piggyback Socket
U1	1	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U2	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License.

6502-ACE

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. Start with Your ACE, the tour of this board.

Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The ACE (All-in-one Computer Experience) is a complete, self-contained 65C02 computer on a single PCB. It integrates everything found across the COB's modular cards — CPU, memory, video, audio, storage, serial, GPIO, RTC, and keyboard controller — onto one board, delivering the full experience without a backplane or expansion cards.

Architecture

All AC6502 computers share:

CPU: 65C02 (or accurate emulation)
Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer (YOU ARE HERE)
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into `.prg` images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the ACE board.

ACE Board

Hardware/ACE Board/

The single integrated board hosting the W65C02S CPU and all peripherals. Provides:

CPU: W65C02S running at 1 or 2 MHz (jumper-selectable)
RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
ROM: 32KB EEPROM (28C256)
Video: Pico9918 (VGA 640×480)
Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
Storage: Storage adapter socket
Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
GPIO: 65C22 VIA (20 GPIO pins, 2× 16-bit timers, shift register)
RTC: DS1511Y real-time clock with battery-backed NVRAM
Keyboard Controller: ATmega1284P running AB Controller firmware
Input: PS/2 keyboard connector and 8×8 keyboard matrix header
Joystick: Two Atari 2600-compatible joystick ports (J6 JOYSTICK A on VIA PORT A, J8 JOYSTICK B on VIA PORT B), read as JOY(2) and JOY(1) respectively
Clock: 16 MHz DIP-14 full can oscillator (X1); drives the ATmega1284 at 16 MHz and the 65C02 at 1 or 2 MHz via the 74HC163 divider (J1 PHI2 SELECT jumper)
Reset: Manual reset button (SW17, just above Esc) connected to the ATmega1284, which also provides power-on reset to the 65C02
Power: 5V DC via barrel jack

Revision History

Rev 1.1

Fixes the gating of the LOADL and LOADH latch-enable signals for the 74HC573 latches (U21, U22) that drive the AS6C4008 banked SRAM. In Rev 1.0 the final two decode gates (U13C/U13D) were NANDs, which left the latches pulsing while idle and allowed spurious loads on reads, so the latches never reliably held a bank value.
The fix replaces the final NAND stage with a NOR function: LOADL = NOR(SEL_L, WB) and LOADH = NOR(SEH_L, WB), holding each latch enable low out of window and only pulsing on an in-window write. This makes banked RAM work correctly with no firmware change.
Implemented by adding one 74HC02 quad NOR (U23). The existing select logic in U13A/U13B is unchanged.
Some pull-up resistors changed from 1kΩ to 10kΩ: R1–R4 and R25 are now 10kΩ.
Added C31 (10µF electrolytic) at the power input for bulk decoupling capacitance.

Rev 1.0

Initial release.

ACE CF Adapter

Hardware/ACE CF Adapter/

A CompactFlash adapter board that connects to the Storage header on the ACE Board. Provides:

Interface: 8-bit IDE (True IDE) mode
Storage: CompactFlash socket. The BIOS filesystem divides the card into 256 disk banks of 1 MB each, so 256 MB is the usable capacity regardless of the card fitted

ACE RAM Patch

Hardware/ACE RAM Patch/

A piggyback patch board for Rev 1.0 of the ACE Board that corrects the extended RAM (banked SRAM) issue. Installs by plugging into the U13 (74HC00) socket on the main board. Provides:

Fix: Replaces the Rev 1.0 NAND-based latch-enable logic with a NOR function (LOADL = NOR(SEL_L, WB), LOADH = NOR(SEH_L, WB)), preventing spurious latch pulses and making banked RAM work correctly with no firmware change
Interface: DIP-14 piggyback connector into U13 on the Rev 1.0 ACE Board

Firmware

This repository contains PlatformIO-based firmware for the ACE board.

AB Controller

Firmware/AB Controller/

Firmware for the ATmega1284P keyboard controller on the ACE board. Provides:

Dual keyboard input: PS/2 and 8×8 matrix keyboard simultaneously
PS/2 scancode to ASCII conversion
Matrix keyboard scanning with hardware debouncing
Modifier key support: Shift (symbols/punctuation) and Ctrl (control codes)
Buffered output via 65C22 VIA with CA1/CB1 data-ready strobes
Independent enable/disable for PS/2 and matrix inputs, releasing PORT A / PORT B so the 6502 can read the joysticks that share them
6502 reset control: drives RESB on PC7, holding the CPU in reset for ~250 ms at power-on, and debounces the reset button on PC0
Optional jiffy clock: pulses NMIB from the DS1511Y SQW input; compiled out unless ENABLE_SQW is defined

See Firmware/AB Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure bases and laser-cut top panels for the ACE system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for the ACE board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

ACE Board

Reference	Qty	Value	Description	DigiKey	Mouser	Other
BT1	1	CR2032	Battery Holder	BAT-HLD-001-THM-ND	712-BAT-HLD-001-THM
C1, C9–C30	23	100nF	Disc Capacitor	478-5732-ND		AMAZON
C2, C3, C5, C6, C8	5	1µF	Disc Capacitor	478-7667-ND		AMAZON
C4, C7	2	2.2nF	Disc Capacitor	478-SR151C222KAATR1CT-ND		AMAZON
C31	1	10uF	Electrolytic Capacitor 16v	P966-ND		AMAZON
D1	1	LED	3.0mm Power LED	732-5008-ND		AMAZON
D2, D3	2	BAT85	Schottky Diode	BAT85SCT-ND	78-BAT85S	AMAZON
J1	1	PHI2 SELECT	Pin Header 1×3 2.54mm			AMAZON
J2	1	CTS EN	Pin Header 1×3 2.54mm			AMAZON
J3	1	RESET SW	Pin Header 1×2 2.54mm			AMAZON
J4	1	DCD EN	Pin Header 1×3 2.54mm			AMAZON
J5	1	VDD	Pin Header 1×2 2.54mm			AMAZON
J6	1	JOYSTICK A	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J7	1	PADDLES	Pin Header 1×4 2.54mm			AMAZON
J8	1	JOYSTICK B	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J9	1	PORT B	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J10	1	PORT A	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J11	1	AUDIO L	RCA Jack	PJRAN1X1U02X-ND	502-PJRAN1X1U02X
J12	1	DB9 MALE (DTE)	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J13	1	PS/2	6-pin Mini-DIN		806-KMDGX-6S-BS	AMAZON
J14	1	KEYBOARD	Pin Header 1×16 2.00mm			AMAZON
J15	1	AUDIO R	RCA Jack	PJRAN1X1U03X-ND	502-PJRAN1X1U03X
J16	1	AUDIO	Pin Header 1×2 2.54mm			AMAZON
J17	1	5V DC	DC Barrel Jack	2073-DCJ200-10-A-K1-K-ND	640-DCJ200-10-A-K1-K
J18	1	CART	Card Edge 2×20 2.54mm	A31723-ND	571-5-5530843-4
J19	1	BUS	Box Header 2×20 2.54mm			AMAZON
J20	1	VCC	Pin Header 1×2 2.54mm			AMAZON
J21	1	POWER LED	Pin Header 1×2 2.54mm			AMAZON
J22	1	STORAGE	Pin Socket 2×10 2.54mm Horiz	S5563-ND
R1–R4, R25	5	10kΩ	1/8W Resistor	RNF18FTD10K0CT-ND		AMAZON
R5–R23, R26–R34	28	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND		AMAZON
R24	1	330Ω	1/8W Resistor			AMAZON
SW1–SW13, SW15, SW18–SW29, SW31, SW33–SW41, SW43, SW44, SW46–SW49, SW51–SW58, SW61, SW64–SW66	54	Various	Cherry MX Switch 1.00u	CH196-ND		AMAZON
SW59, SW60, SW63, SW67, SW68	5	CTRL / ALT / FN	Cherry MX Switch 1.25u	CH196-ND		AMAZON
SW16, SW30	2	TAB / Backslash	Cherry MX Switch 1.50u	CH196-ND		AMAZON
SW32	1	CAPS LOCK	Cherry MX Switch 1.75u	CH196-ND		AMAZON
SW14	1	BACKSPACE	Cherry MX Switch 2.00u	CH196-ND		AMAZON
SW42, SW45, SW50	3	SHIFT / ENTER	Cherry MX Switch 2.25u	CH196-ND		AMAZON
SW62	1	SPACE	Cherry MX Switch 6.25u	CH196-ND		AMAZON
SW17	1	RESET	Tact Push Button 6mm			AMAZON
SW69	1	POWER	SPDT Switch	EG4326-ND	612-400MSP1R6BLKM6QE
SW70	1	IO ENABLE	8× DIP Switch SPST			AMAZON
U1	1	W65C02S	65C02 CPU		955-W65C02S6TPG-14
U2	1	W65C22	65C22 VIA		955-W65C22N6TPG-14
U3	1	Pico9918A	VDP (VGA)			TINDIE
U4	1	65C51	ACIA			JAMECO
U5	1	74HC163	4-bit Counter	296-8246-5-ND	595-SN74HC163N
U6	1	ATmega1284-P	Keyboard Controller MCU	ATMEGA1284-PU-ND	556-ATMEGA1284-PU
U7	1	AS6C62256	32KB SRAM	1450-1033-ND	913-AS6C62256-55PCN
U8	1	AT28C256	32KB EEPROM	AT28C256-15PU-ND	556-AT28C25615PU
U9	1	6581	SID Chip			LINK
U10	1	MAX238xNG+	RS-232 Transceiver	MAX238CNG+-ND	700-MAX238CNG
U11–U14, U16	5	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U15	1	AS6C4008	512KB SRAM	1450-1027-ND	913-AS6C4008-55PCN
U17	1	74HC30	8-input NAND	296-9196-5-ND	595-CD74HC30E
U18	1	DS1511Y	RTC + NVRAM	DS1511Y+-ND	700-DS1511Y
U19, U20	2	74HC138	3-to-8 Decoder	296-1575-5-ND	595-SN74HC138N
U21, U22	2	74HC573	Octal Latch	296-12815-5-ND	595-CD74HC573EE4
U23	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N
X1	1	16MHz	DIP-14 Oscillator	X947-ND	815-ACO-16-EK
Y1	1	1.8432MHz	Crystal	3155-1.8432M20P2/49U-ND	815-AB-1.8432-B2

ACE CF Adapter

Reference	Qty	Value	Description	DigiKey	Other
D1	1	ACT LED	3.0mm LED	732-5008-ND	AMAZON
J1	1	STORAGE	Pin Header 2×10 2.54mm Horiz		AMAZON
J2	1	Compact Flash	CF Socket	4827-101D-TAAB-R01-ND
R1–R4	4	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND	AMAZON
R5	1	330Ω	1/8W Resistor		AMAZON

ACE RAM Patch

Reference	Qty	Value	Description	DigiKey	Mouser
J1	1	74HC00 (U13)	DIP-14 Piggyback Socket
U1	1	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U2	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License.

6502-ACE

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. Start with Your ACE, the tour of this board.

Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The ACE (All-in-one Computer Experience) is a complete, self-contained 65C02 computer on a single PCB. It integrates everything found across the COB's modular cards — CPU, memory, video, audio, storage, serial, GPIO, RTC, and keyboard controller — onto one board, delivering the full experience without a backplane or expansion cards.

Architecture

All AC6502 computers share:

CPU: 65C02 (or accurate emulation)
Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer (YOU ARE HERE)
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into `.prg` images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the ACE board.

ACE Board

Hardware/ACE Board/

The single integrated board hosting the W65C02S CPU and all peripherals. Provides:

CPU: W65C02S running at 1 or 2 MHz (jumper-selectable)
RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
ROM: 32KB EEPROM (28C256)
Video: Pico9918 (VGA 640×480)
Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
Storage: Storage adapter socket
Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
GPIO: 65C22 VIA (20 GPIO pins, 2× 16-bit timers, shift register)
RTC: DS1511Y real-time clock with battery-backed NVRAM
Keyboard Controller: ATmega1284P running AB Controller firmware
Input: PS/2 keyboard connector and 8×8 keyboard matrix header
Joystick: Two Atari 2600-compatible joystick ports (J6 JOYSTICK A on VIA PORT A, J8 JOYSTICK B on VIA PORT B), read as JOY(2) and JOY(1) respectively
Clock: 16 MHz DIP-14 full can oscillator (X1); drives the ATmega1284 at 16 MHz and the 65C02 at 1 or 2 MHz via the 74HC163 divider (J1 PHI2 SELECT jumper)
Reset: Manual reset button (SW17, just above Esc) connected to the ATmega1284, which also provides power-on reset to the 65C02
Power: 5V DC via barrel jack

Revision History

Rev 1.1

Fixes the gating of the LOADL and LOADH latch-enable signals for the 74HC573 latches (U21, U22) that drive the AS6C4008 banked SRAM. In Rev 1.0 the final two decode gates (U13C/U13D) were NANDs, which left the latches pulsing while idle and allowed spurious loads on reads, so the latches never reliably held a bank value.
The fix replaces the final NAND stage with a NOR function: LOADL = NOR(SEL_L, WB) and LOADH = NOR(SEH_L, WB), holding each latch enable low out of window and only pulsing on an in-window write. This makes banked RAM work correctly with no firmware change.
Implemented by adding one 74HC02 quad NOR (U23). The existing select logic in U13A/U13B is unchanged.
Some pull-up resistors changed from 1kΩ to 10kΩ: R1–R4 and R25 are now 10kΩ.
Added C31 (10µF electrolytic) at the power input for bulk decoupling capacitance.

Rev 1.0

Initial release.

ACE CF Adapter

Hardware/ACE CF Adapter/

A CompactFlash adapter board that connects to the Storage header on the ACE Board. Provides:

Interface: 8-bit IDE (True IDE) mode
Storage: CompactFlash socket. The BIOS filesystem divides the card into 256 disk banks of 1 MB each, so 256 MB is the usable capacity regardless of the card fitted

ACE RAM Patch

Hardware/ACE RAM Patch/

A piggyback patch board for Rev 1.0 of the ACE Board that corrects the extended RAM (banked SRAM) issue. Installs by plugging into the U13 (74HC00) socket on the main board. Provides:

Fix: Replaces the Rev 1.0 NAND-based latch-enable logic with a NOR function (LOADL = NOR(SEL_L, WB), LOADH = NOR(SEH_L, WB)), preventing spurious latch pulses and making banked RAM work correctly with no firmware change
Interface: DIP-14 piggyback connector into U13 on the Rev 1.0 ACE Board

Firmware

This repository contains PlatformIO-based firmware for the ACE board.

AB Controller

Firmware/AB Controller/

Firmware for the ATmega1284P keyboard controller on the ACE board. Provides:

Dual keyboard input: PS/2 and 8×8 matrix keyboard simultaneously
PS/2 scancode to ASCII conversion
Matrix keyboard scanning with hardware debouncing
Modifier key support: Shift (symbols/punctuation) and Ctrl (control codes)
Buffered output via 65C22 VIA with CA1/CB1 data-ready strobes
Independent enable/disable for PS/2 and matrix inputs, releasing PORT A / PORT B so the 6502 can read the joysticks that share them
6502 reset control: drives RESB on PC7, holding the CPU in reset for ~250 ms at power-on, and debounces the reset button on PC0
Optional jiffy clock: pulses NMIB from the DS1511Y SQW input; compiled out unless ENABLE_SQW is defined

See Firmware/AB Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure bases and laser-cut top panels for the ACE system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for the ACE board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

ACE Board

Reference	Qty	Value	Description	DigiKey	Mouser	Other
BT1	1	CR2032	Battery Holder	BAT-HLD-001-THM-ND	712-BAT-HLD-001-THM
C1, C9–C30	23	100nF	Disc Capacitor	478-5732-ND		AMAZON
C2, C3, C5, C6, C8	5	1µF	Disc Capacitor	478-7667-ND		AMAZON
C4, C7	2	2.2nF	Disc Capacitor	478-SR151C222KAATR1CT-ND		AMAZON
C31	1	10uF	Electrolytic Capacitor 16v	P966-ND		AMAZON
D1	1	LED	3.0mm Power LED	732-5008-ND		AMAZON
D2, D3	2	BAT85	Schottky Diode	BAT85SCT-ND	78-BAT85S	AMAZON
J1	1	PHI2 SELECT	Pin Header 1×3 2.54mm			AMAZON
J2	1	CTS EN	Pin Header 1×3 2.54mm			AMAZON
J3	1	RESET SW	Pin Header 1×2 2.54mm			AMAZON
J4	1	DCD EN	Pin Header 1×3 2.54mm			AMAZON
J5	1	VDD	Pin Header 1×2 2.54mm			AMAZON
J6	1	JOYSTICK A	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J7	1	PADDLES	Pin Header 1×4 2.54mm			AMAZON
J8	1	JOYSTICK B	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J9	1	PORT B	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J10	1	PORT A	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J11	1	AUDIO L	RCA Jack	PJRAN1X1U02X-ND	502-PJRAN1X1U02X
J12	1	DB9 MALE (DTE)	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J13	1	PS/2	6-pin Mini-DIN		806-KMDGX-6S-BS	AMAZON
J14	1	KEYBOARD	Pin Header 1×16 2.00mm			AMAZON
J15	1	AUDIO R	RCA Jack	PJRAN1X1U03X-ND	502-PJRAN1X1U03X
J16	1	AUDIO	Pin Header 1×2 2.54mm			AMAZON
J17	1	5V DC	DC Barrel Jack	2073-DCJ200-10-A-K1-K-ND	640-DCJ200-10-A-K1-K
J18	1	CART	Card Edge 2×20 2.54mm	A31723-ND	571-5-5530843-4
J19	1	BUS	Box Header 2×20 2.54mm			AMAZON
J20	1	VCC	Pin Header 1×2 2.54mm			AMAZON
J21	1	POWER LED	Pin Header 1×2 2.54mm			AMAZON
J22	1	STORAGE	Pin Socket 2×10 2.54mm Horiz	S5563-ND
R1–R4, R25	5	10kΩ	1/8W Resistor	RNF18FTD10K0CT-ND		AMAZON
R5–R23, R26–R34	28	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND		AMAZON
R24	1	330Ω	1/8W Resistor			AMAZON
SW1–SW13, SW15, SW18–SW29, SW31, SW33–SW41, SW43, SW44, SW46–SW49, SW51–SW58, SW61, SW64–SW66	54	Various	Cherry MX Switch 1.00u	CH196-ND		AMAZON
SW59, SW60, SW63, SW67, SW68	5	CTRL / ALT / FN	Cherry MX Switch 1.25u	CH196-ND		AMAZON
SW16, SW30	2	TAB / Backslash	Cherry MX Switch 1.50u	CH196-ND		AMAZON
SW32	1	CAPS LOCK	Cherry MX Switch 1.75u	CH196-ND		AMAZON
SW14	1	BACKSPACE	Cherry MX Switch 2.00u	CH196-ND		AMAZON
SW42, SW45, SW50	3	SHIFT / ENTER	Cherry MX Switch 2.25u	CH196-ND		AMAZON
SW62	1	SPACE	Cherry MX Switch 6.25u	CH196-ND		AMAZON
SW17	1	RESET	Tact Push Button 6mm			AMAZON
SW69	1	POWER	SPDT Switch	EG4326-ND	612-400MSP1R6BLKM6QE
SW70	1	IO ENABLE	8× DIP Switch SPST			AMAZON
U1	1	W65C02S	65C02 CPU		955-W65C02S6TPG-14
U2	1	W65C22	65C22 VIA		955-W65C22N6TPG-14
U3	1	Pico9918A	VDP (VGA)			TINDIE
U4	1	65C51	ACIA			JAMECO
U5	1	74HC163	4-bit Counter	296-8246-5-ND	595-SN74HC163N
U6	1	ATmega1284-P	Keyboard Controller MCU	ATMEGA1284-PU-ND	556-ATMEGA1284-PU
U7	1	AS6C62256	32KB SRAM	1450-1033-ND	913-AS6C62256-55PCN
U8	1	AT28C256	32KB EEPROM	AT28C256-15PU-ND	556-AT28C25615PU
U9	1	6581	SID Chip			LINK
U10	1	MAX238xNG+	RS-232 Transceiver	MAX238CNG+-ND	700-MAX238CNG
U11–U14, U16	5	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U15	1	AS6C4008	512KB SRAM	1450-1027-ND	913-AS6C4008-55PCN
U17	1	74HC30	8-input NAND	296-9196-5-ND	595-CD74HC30E
U18	1	DS1511Y	RTC + NVRAM	DS1511Y+-ND	700-DS1511Y
U19, U20	2	74HC138	3-to-8 Decoder	296-1575-5-ND	595-SN74HC138N
U21, U22	2	74HC573	Octal Latch	296-12815-5-ND	595-CD74HC573EE4
U23	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N
X1	1	16MHz	DIP-14 Oscillator	X947-ND	815-ACO-16-EK
Y1	1	1.8432MHz	Crystal	3155-1.8432M20P2/49U-ND	815-AB-1.8432-B2

ACE CF Adapter

Reference	Qty	Value	Description	DigiKey	Other
D1	1	ACT LED	3.0mm LED	732-5008-ND	AMAZON
J1	1	STORAGE	Pin Header 2×10 2.54mm Horiz		AMAZON
J2	1	Compact Flash	CF Socket	4827-101D-TAAB-R01-ND
R1–R4	4	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND	AMAZON
R5	1	330Ω	1/8W Resistor		AMAZON

ACE RAM Patch

Reference	Qty	Value	Description	DigiKey	Mouser
J1	1	74HC00 (U13)	DIP-14 Piggyback Socket
U1	1	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U2	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License.

6502-ACE

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. Start with Your ACE, the tour of this board.

Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The ACE (All-in-one Computer Experience) is a complete, self-contained 65C02 computer on a single PCB. It integrates everything found across the COB's modular cards — CPU, memory, video, audio, storage, serial, GPIO, RTC, and keyboard controller — onto one board, delivering the full experience without a backplane or expansion cards.

Architecture

All AC6502 computers share:

CPU: 65C02 (or accurate emulation)
Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer (YOU ARE HERE)
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into `.prg` images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the ACE board.

ACE Board

Hardware/ACE Board/

The single integrated board hosting the W65C02S CPU and all peripherals. Provides:

CPU: W65C02S running at 1 or 2 MHz (jumper-selectable)
RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
ROM: 32KB EEPROM (28C256)
Video: Pico9918 (VGA 640×480)
Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
Storage: Storage adapter socket
Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
GPIO: 65C22 VIA (20 GPIO pins, 2× 16-bit timers, shift register)
RTC: DS1511Y real-time clock with battery-backed NVRAM
Keyboard Controller: ATmega1284P running AB Controller firmware
Input: PS/2 keyboard connector and 8×8 keyboard matrix header
Joystick: Two Atari 2600-compatible joystick ports (J6 JOYSTICK A on VIA PORT A, J8 JOYSTICK B on VIA PORT B), read as JOY(2) and JOY(1) respectively
Clock: 16 MHz DIP-14 full can oscillator (X1); drives the ATmega1284 at 16 MHz and the 65C02 at 1 or 2 MHz via the 74HC163 divider (J1 PHI2 SELECT jumper)
Reset: Manual reset button (SW17, just above Esc) connected to the ATmega1284, which also provides power-on reset to the 65C02
Power: 5V DC via barrel jack

Revision History

Rev 1.1

Fixes the gating of the LOADL and LOADH latch-enable signals for the 74HC573 latches (U21, U22) that drive the AS6C4008 banked SRAM. In Rev 1.0 the final two decode gates (U13C/U13D) were NANDs, which left the latches pulsing while idle and allowed spurious loads on reads, so the latches never reliably held a bank value.
The fix replaces the final NAND stage with a NOR function: LOADL = NOR(SEL_L, WB) and LOADH = NOR(SEH_L, WB), holding each latch enable low out of window and only pulsing on an in-window write. This makes banked RAM work correctly with no firmware change.
Implemented by adding one 74HC02 quad NOR (U23). The existing select logic in U13A/U13B is unchanged.
Some pull-up resistors changed from 1kΩ to 10kΩ: R1–R4 and R25 are now 10kΩ.
Added C31 (10µF electrolytic) at the power input for bulk decoupling capacitance.

Rev 1.0

Initial release.

ACE CF Adapter

Hardware/ACE CF Adapter/

A CompactFlash adapter board that connects to the Storage header on the ACE Board. Provides:

Interface: 8-bit IDE (True IDE) mode
Storage: CompactFlash socket. The BIOS filesystem divides the card into 256 disk banks of 1 MB each, so 256 MB is the usable capacity regardless of the card fitted

ACE RAM Patch

Hardware/ACE RAM Patch/

A piggyback patch board for Rev 1.0 of the ACE Board that corrects the extended RAM (banked SRAM) issue. Installs by plugging into the U13 (74HC00) socket on the main board. Provides:

Fix: Replaces the Rev 1.0 NAND-based latch-enable logic with a NOR function (LOADL = NOR(SEL_L, WB), LOADH = NOR(SEH_L, WB)), preventing spurious latch pulses and making banked RAM work correctly with no firmware change
Interface: DIP-14 piggyback connector into U13 on the Rev 1.0 ACE Board

Firmware

This repository contains PlatformIO-based firmware for the ACE board.

AB Controller

Firmware/AB Controller/

Firmware for the ATmega1284P keyboard controller on the ACE board. Provides:

Dual keyboard input: PS/2 and 8×8 matrix keyboard simultaneously
PS/2 scancode to ASCII conversion
Matrix keyboard scanning with hardware debouncing
Modifier key support: Shift (symbols/punctuation) and Ctrl (control codes)
Buffered output via 65C22 VIA with CA1/CB1 data-ready strobes
Independent enable/disable for PS/2 and matrix inputs, releasing PORT A / PORT B so the 6502 can read the joysticks that share them
6502 reset control: drives RESB on PC7, holding the CPU in reset for ~250 ms at power-on, and debounces the reset button on PC0
Optional jiffy clock: pulses NMIB from the DS1511Y SQW input; compiled out unless ENABLE_SQW is defined

See Firmware/AB Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure bases and laser-cut top panels for the ACE system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for the ACE board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

ACE Board

Reference	Qty	Value	Description	DigiKey	Mouser	Other
BT1	1	CR2032	Battery Holder	BAT-HLD-001-THM-ND	712-BAT-HLD-001-THM
C1, C9–C30	23	100nF	Disc Capacitor	478-5732-ND		AMAZON
C2, C3, C5, C6, C8	5	1µF	Disc Capacitor	478-7667-ND		AMAZON
C4, C7	2	2.2nF	Disc Capacitor	478-SR151C222KAATR1CT-ND		AMAZON
C31	1	10uF	Electrolytic Capacitor 16v	P966-ND		AMAZON
D1	1	LED	3.0mm Power LED	732-5008-ND		AMAZON
D2, D3	2	BAT85	Schottky Diode	BAT85SCT-ND	78-BAT85S	AMAZON
J1	1	PHI2 SELECT	Pin Header 1×3 2.54mm			AMAZON
J2	1	CTS EN	Pin Header 1×3 2.54mm			AMAZON
J3	1	RESET SW	Pin Header 1×2 2.54mm			AMAZON
J4	1	DCD EN	Pin Header 1×3 2.54mm			AMAZON
J5	1	VDD	Pin Header 1×2 2.54mm			AMAZON
J6	1	JOYSTICK A	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J7	1	PADDLES	Pin Header 1×4 2.54mm			AMAZON
J8	1	JOYSTICK B	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J9	1	PORT B	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J10	1	PORT A	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J11	1	AUDIO L	RCA Jack	PJRAN1X1U02X-ND	502-PJRAN1X1U02X
J12	1	DB9 MALE (DTE)	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J13	1	PS/2	6-pin Mini-DIN		806-KMDGX-6S-BS	AMAZON
J14	1	KEYBOARD	Pin Header 1×16 2.00mm			AMAZON
J15	1	AUDIO R	RCA Jack	PJRAN1X1U03X-ND	502-PJRAN1X1U03X
J16	1	AUDIO	Pin Header 1×2 2.54mm			AMAZON
J17	1	5V DC	DC Barrel Jack	2073-DCJ200-10-A-K1-K-ND	640-DCJ200-10-A-K1-K
J18	1	CART	Card Edge 2×20 2.54mm	A31723-ND	571-5-5530843-4
J19	1	BUS	Box Header 2×20 2.54mm			AMAZON
J20	1	VCC	Pin Header 1×2 2.54mm			AMAZON
J21	1	POWER LED	Pin Header 1×2 2.54mm			AMAZON
J22	1	STORAGE	Pin Socket 2×10 2.54mm Horiz	S5563-ND
R1–R4, R25	5	10kΩ	1/8W Resistor	RNF18FTD10K0CT-ND		AMAZON
R5–R23, R26–R34	28	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND		AMAZON
R24	1	330Ω	1/8W Resistor			AMAZON
SW1–SW13, SW15, SW18–SW29, SW31, SW33–SW41, SW43, SW44, SW46–SW49, SW51–SW58, SW61, SW64–SW66	54	Various	Cherry MX Switch 1.00u	CH196-ND		AMAZON
SW59, SW60, SW63, SW67, SW68	5	CTRL / ALT / FN	Cherry MX Switch 1.25u	CH196-ND		AMAZON
SW16, SW30	2	TAB / Backslash	Cherry MX Switch 1.50u	CH196-ND		AMAZON
SW32	1	CAPS LOCK	Cherry MX Switch 1.75u	CH196-ND		AMAZON
SW14	1	BACKSPACE	Cherry MX Switch 2.00u	CH196-ND		AMAZON
SW42, SW45, SW50	3	SHIFT / ENTER	Cherry MX Switch 2.25u	CH196-ND		AMAZON
SW62	1	SPACE	Cherry MX Switch 6.25u	CH196-ND		AMAZON
SW17	1	RESET	Tact Push Button 6mm			AMAZON
SW69	1	POWER	SPDT Switch	EG4326-ND	612-400MSP1R6BLKM6QE
SW70	1	IO ENABLE	8× DIP Switch SPST			AMAZON
U1	1	W65C02S	65C02 CPU		955-W65C02S6TPG-14
U2	1	W65C22	65C22 VIA		955-W65C22N6TPG-14
U3	1	Pico9918A	VDP (VGA)			TINDIE
U4	1	65C51	ACIA			JAMECO
U5	1	74HC163	4-bit Counter	296-8246-5-ND	595-SN74HC163N
U6	1	ATmega1284-P	Keyboard Controller MCU	ATMEGA1284-PU-ND	556-ATMEGA1284-PU
U7	1	AS6C62256	32KB SRAM	1450-1033-ND	913-AS6C62256-55PCN
U8	1	AT28C256	32KB EEPROM	AT28C256-15PU-ND	556-AT28C25615PU
U9	1	6581	SID Chip			LINK
U10	1	MAX238xNG+	RS-232 Transceiver	MAX238CNG+-ND	700-MAX238CNG
U11–U14, U16	5	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U15	1	AS6C4008	512KB SRAM	1450-1027-ND	913-AS6C4008-55PCN
U17	1	74HC30	8-input NAND	296-9196-5-ND	595-CD74HC30E
U18	1	DS1511Y	RTC + NVRAM	DS1511Y+-ND	700-DS1511Y
U19, U20	2	74HC138	3-to-8 Decoder	296-1575-5-ND	595-SN74HC138N
U21, U22	2	74HC573	Octal Latch	296-12815-5-ND	595-CD74HC573EE4
U23	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N
X1	1	16MHz	DIP-14 Oscillator	X947-ND	815-ACO-16-EK
Y1	1	1.8432MHz	Crystal	3155-1.8432M20P2/49U-ND	815-AB-1.8432-B2

ACE CF Adapter

Reference	Qty	Value	Description	DigiKey	Other
D1	1	ACT LED	3.0mm LED	732-5008-ND	AMAZON
J1	1	STORAGE	Pin Header 2×10 2.54mm Horiz		AMAZON
J2	1	Compact Flash	CF Socket	4827-101D-TAAB-R01-ND
R1–R4	4	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND	AMAZON
R5	1	330Ω	1/8W Resistor		AMAZON

ACE RAM Patch

Reference	Qty	Value	Description	DigiKey	Mouser
J1	1	74HC00 (U13)	DIP-14 Piggyback Socket
U1	1	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U2	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License.

6502-ACE

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. Start with Your ACE, the tour of this board.

Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The ACE (All-in-one Computer Experience) is a complete, self-contained 65C02 computer on a single PCB. It integrates everything found across the COB's modular cards — CPU, memory, video, audio, storage, serial, GPIO, RTC, and keyboard controller — onto one board, delivering the full experience without a backplane or expansion cards.

Architecture

All AC6502 computers share:

CPU: 65C02 (or accurate emulation)
Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer (YOU ARE HERE)
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into `.prg` images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the ACE board.

ACE Board

Hardware/ACE Board/

The single integrated board hosting the W65C02S CPU and all peripherals. Provides:

CPU: W65C02S running at 1 or 2 MHz (jumper-selectable)
RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
ROM: 32KB EEPROM (28C256)
Video: Pico9918 (VGA 640×480)
Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
Storage: Storage adapter socket
Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
GPIO: 65C22 VIA (20 GPIO pins, 2× 16-bit timers, shift register)
RTC: DS1511Y real-time clock with battery-backed NVRAM
Keyboard Controller: ATmega1284P running AB Controller firmware
Input: PS/2 keyboard connector and 8×8 keyboard matrix header
Joystick: Two Atari 2600-compatible joystick ports (J6 JOYSTICK A on VIA PORT A, J8 JOYSTICK B on VIA PORT B), read as JOY(2) and JOY(1) respectively
Clock: 16 MHz DIP-14 full can oscillator (X1); drives the ATmega1284 at 16 MHz and the 65C02 at 1 or 2 MHz via the 74HC163 divider (J1 PHI2 SELECT jumper)
Reset: Manual reset button (SW17, just above Esc) connected to the ATmega1284, which also provides power-on reset to the 65C02
Power: 5V DC via barrel jack

Revision History

Rev 1.1

Fixes the gating of the LOADL and LOADH latch-enable signals for the 74HC573 latches (U21, U22) that drive the AS6C4008 banked SRAM. In Rev 1.0 the final two decode gates (U13C/U13D) were NANDs, which left the latches pulsing while idle and allowed spurious loads on reads, so the latches never reliably held a bank value.
The fix replaces the final NAND stage with a NOR function: LOADL = NOR(SEL_L, WB) and LOADH = NOR(SEH_L, WB), holding each latch enable low out of window and only pulsing on an in-window write. This makes banked RAM work correctly with no firmware change.
Implemented by adding one 74HC02 quad NOR (U23). The existing select logic in U13A/U13B is unchanged.
Some pull-up resistors changed from 1kΩ to 10kΩ: R1–R4 and R25 are now 10kΩ.
Added C31 (10µF electrolytic) at the power input for bulk decoupling capacitance.

Rev 1.0

Initial release.

ACE CF Adapter

Hardware/ACE CF Adapter/

A CompactFlash adapter board that connects to the Storage header on the ACE Board. Provides:

Interface: 8-bit IDE (True IDE) mode
Storage: CompactFlash socket. The BIOS filesystem divides the card into 256 disk banks of 1 MB each, so 256 MB is the usable capacity regardless of the card fitted

ACE RAM Patch

Hardware/ACE RAM Patch/

A piggyback patch board for Rev 1.0 of the ACE Board that corrects the extended RAM (banked SRAM) issue. Installs by plugging into the U13 (74HC00) socket on the main board. Provides:

Fix: Replaces the Rev 1.0 NAND-based latch-enable logic with a NOR function (LOADL = NOR(SEL_L, WB), LOADH = NOR(SEH_L, WB)), preventing spurious latch pulses and making banked RAM work correctly with no firmware change
Interface: DIP-14 piggyback connector into U13 on the Rev 1.0 ACE Board

Firmware

This repository contains PlatformIO-based firmware for the ACE board.

AB Controller

Firmware/AB Controller/

Firmware for the ATmega1284P keyboard controller on the ACE board. Provides:

Dual keyboard input: PS/2 and 8×8 matrix keyboard simultaneously
PS/2 scancode to ASCII conversion
Matrix keyboard scanning with hardware debouncing
Modifier key support: Shift (symbols/punctuation) and Ctrl (control codes)
Buffered output via 65C22 VIA with CA1/CB1 data-ready strobes
Independent enable/disable for PS/2 and matrix inputs, releasing PORT A / PORT B so the 6502 can read the joysticks that share them
6502 reset control: drives RESB on PC7, holding the CPU in reset for ~250 ms at power-on, and debounces the reset button on PC0
Optional jiffy clock: pulses NMIB from the DS1511Y SQW input; compiled out unless ENABLE_SQW is defined

See Firmware/AB Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure bases and laser-cut top panels for the ACE system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for the ACE board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

ACE Board

Reference	Qty	Value	Description	DigiKey	Mouser	Other
BT1	1	CR2032	Battery Holder	BAT-HLD-001-THM-ND	712-BAT-HLD-001-THM
C1, C9–C30	23	100nF	Disc Capacitor	478-5732-ND		AMAZON
C2, C3, C5, C6, C8	5	1µF	Disc Capacitor	478-7667-ND		AMAZON
C4, C7	2	2.2nF	Disc Capacitor	478-SR151C222KAATR1CT-ND		AMAZON
C31	1	10uF	Electrolytic Capacitor 16v	P966-ND		AMAZON
D1	1	LED	3.0mm Power LED	732-5008-ND		AMAZON
D2, D3	2	BAT85	Schottky Diode	BAT85SCT-ND	78-BAT85S	AMAZON
J1	1	PHI2 SELECT	Pin Header 1×3 2.54mm			AMAZON
J2	1	CTS EN	Pin Header 1×3 2.54mm			AMAZON
J3	1	RESET SW	Pin Header 1×2 2.54mm			AMAZON
J4	1	DCD EN	Pin Header 1×3 2.54mm			AMAZON
J5	1	VDD	Pin Header 1×2 2.54mm			AMAZON
J6	1	JOYSTICK A	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J7	1	PADDLES	Pin Header 1×4 2.54mm			AMAZON
J8	1	JOYSTICK B	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J9	1	PORT B	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J10	1	PORT A	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J11	1	AUDIO L	RCA Jack	PJRAN1X1U02X-ND	502-PJRAN1X1U02X
J12	1	DB9 MALE (DTE)	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J13	1	PS/2	6-pin Mini-DIN		806-KMDGX-6S-BS	AMAZON
J14	1	KEYBOARD	Pin Header 1×16 2.00mm			AMAZON
J15	1	AUDIO R	RCA Jack	PJRAN1X1U03X-ND	502-PJRAN1X1U03X
J16	1	AUDIO	Pin Header 1×2 2.54mm			AMAZON
J17	1	5V DC	DC Barrel Jack	2073-DCJ200-10-A-K1-K-ND	640-DCJ200-10-A-K1-K
J18	1	CART	Card Edge 2×20 2.54mm	A31723-ND	571-5-5530843-4
J19	1	BUS	Box Header 2×20 2.54mm			AMAZON
J20	1	VCC	Pin Header 1×2 2.54mm			AMAZON
J21	1	POWER LED	Pin Header 1×2 2.54mm			AMAZON
J22	1	STORAGE	Pin Socket 2×10 2.54mm Horiz	S5563-ND
R1–R4, R25	5	10kΩ	1/8W Resistor	RNF18FTD10K0CT-ND		AMAZON
R5–R23, R26–R34	28	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND		AMAZON
R24	1	330Ω	1/8W Resistor			AMAZON
SW1–SW13, SW15, SW18–SW29, SW31, SW33–SW41, SW43, SW44, SW46–SW49, SW51–SW58, SW61, SW64–SW66	54	Various	Cherry MX Switch 1.00u	CH196-ND		AMAZON
SW59, SW60, SW63, SW67, SW68	5	CTRL / ALT / FN	Cherry MX Switch 1.25u	CH196-ND		AMAZON
SW16, SW30	2	TAB / Backslash	Cherry MX Switch 1.50u	CH196-ND		AMAZON
SW32	1	CAPS LOCK	Cherry MX Switch 1.75u	CH196-ND		AMAZON
SW14	1	BACKSPACE	Cherry MX Switch 2.00u	CH196-ND		AMAZON
SW42, SW45, SW50	3	SHIFT / ENTER	Cherry MX Switch 2.25u	CH196-ND		AMAZON
SW62	1	SPACE	Cherry MX Switch 6.25u	CH196-ND		AMAZON
SW17	1	RESET	Tact Push Button 6mm			AMAZON
SW69	1	POWER	SPDT Switch	EG4326-ND	612-400MSP1R6BLKM6QE
SW70	1	IO ENABLE	8× DIP Switch SPST			AMAZON
U1	1	W65C02S	65C02 CPU		955-W65C02S6TPG-14
U2	1	W65C22	65C22 VIA		955-W65C22N6TPG-14
U3	1	Pico9918A	VDP (VGA)			TINDIE
U4	1	65C51	ACIA			JAMECO
U5	1	74HC163	4-bit Counter	296-8246-5-ND	595-SN74HC163N
U6	1	ATmega1284-P	Keyboard Controller MCU	ATMEGA1284-PU-ND	556-ATMEGA1284-PU
U7	1	AS6C62256	32KB SRAM	1450-1033-ND	913-AS6C62256-55PCN
U8	1	AT28C256	32KB EEPROM	AT28C256-15PU-ND	556-AT28C25615PU
U9	1	6581	SID Chip			LINK
U10	1	MAX238xNG+	RS-232 Transceiver	MAX238CNG+-ND	700-MAX238CNG
U11–U14, U16	5	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U15	1	AS6C4008	512KB SRAM	1450-1027-ND	913-AS6C4008-55PCN
U17	1	74HC30	8-input NAND	296-9196-5-ND	595-CD74HC30E
U18	1	DS1511Y	RTC + NVRAM	DS1511Y+-ND	700-DS1511Y
U19, U20	2	74HC138	3-to-8 Decoder	296-1575-5-ND	595-SN74HC138N
U21, U22	2	74HC573	Octal Latch	296-12815-5-ND	595-CD74HC573EE4
U23	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N
X1	1	16MHz	DIP-14 Oscillator	X947-ND	815-ACO-16-EK
Y1	1	1.8432MHz	Crystal	3155-1.8432M20P2/49U-ND	815-AB-1.8432-B2

ACE CF Adapter

Reference	Qty	Value	Description	DigiKey	Other
D1	1	ACT LED	3.0mm LED	732-5008-ND	AMAZON
J1	1	STORAGE	Pin Header 2×10 2.54mm Horiz		AMAZON
J2	1	Compact Flash	CF Socket	4827-101D-TAAB-R01-ND
R1–R4	4	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND	AMAZON
R5	1	330Ω	1/8W Resistor		AMAZON

ACE RAM Patch

Reference	Qty	Value	Description	DigiKey	Mouser
J1	1	74HC00 (U13)	DIP-14 Piggyback Socket
U1	1	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U2	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License.

6502-ACE

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. Start with Your ACE, the tour of this board.

Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The ACE (All-in-one Computer Experience) is a complete, self-contained 65C02 computer on a single PCB. It integrates everything found across the COB's modular cards — CPU, memory, video, audio, storage, serial, GPIO, RTC, and keyboard controller — onto one board, delivering the full experience without a backplane or expansion cards.

Architecture

All AC6502 computers share:

CPU: 65C02 (or accurate emulation)
Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer (YOU ARE HERE)
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into `.prg` images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the ACE board.

ACE Board

Hardware/ACE Board/

The single integrated board hosting the W65C02S CPU and all peripherals. Provides:

CPU: W65C02S running at 1 or 2 MHz (jumper-selectable)
RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
ROM: 32KB EEPROM (28C256)
Video: Pico9918 (VGA 640×480)
Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
Storage: Storage adapter socket
Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
GPIO: 65C22 VIA (20 GPIO pins, 2× 16-bit timers, shift register)
RTC: DS1511Y real-time clock with battery-backed NVRAM
Keyboard Controller: ATmega1284P running AB Controller firmware
Input: PS/2 keyboard connector and 8×8 keyboard matrix header
Joystick: Two Atari 2600-compatible joystick ports (J6 JOYSTICK A on VIA PORT A, J8 JOYSTICK B on VIA PORT B), read as JOY(2) and JOY(1) respectively
Clock: 16 MHz DIP-14 full can oscillator (X1); drives the ATmega1284 at 16 MHz and the 65C02 at 1 or 2 MHz via the 74HC163 divider (J1 PHI2 SELECT jumper)
Reset: Manual reset button (SW17, just above Esc) connected to the ATmega1284, which also provides power-on reset to the 65C02
Power: 5V DC via barrel jack

Revision History

Rev 1.1

Fixes the gating of the LOADL and LOADH latch-enable signals for the 74HC573 latches (U21, U22) that drive the AS6C4008 banked SRAM. In Rev 1.0 the final two decode gates (U13C/U13D) were NANDs, which left the latches pulsing while idle and allowed spurious loads on reads, so the latches never reliably held a bank value.
The fix replaces the final NAND stage with a NOR function: LOADL = NOR(SEL_L, WB) and LOADH = NOR(SEH_L, WB), holding each latch enable low out of window and only pulsing on an in-window write. This makes banked RAM work correctly with no firmware change.
Implemented by adding one 74HC02 quad NOR (U23). The existing select logic in U13A/U13B is unchanged.
Some pull-up resistors changed from 1kΩ to 10kΩ: R1–R4 and R25 are now 10kΩ.
Added C31 (10µF electrolytic) at the power input for bulk decoupling capacitance.

Rev 1.0

Initial release.

ACE CF Adapter

Hardware/ACE CF Adapter/

A CompactFlash adapter board that connects to the Storage header on the ACE Board. Provides:

Interface: 8-bit IDE (True IDE) mode
Storage: CompactFlash socket. The BIOS filesystem divides the card into 256 disk banks of 1 MB each, so 256 MB is the usable capacity regardless of the card fitted

ACE RAM Patch

Hardware/ACE RAM Patch/

A piggyback patch board for Rev 1.0 of the ACE Board that corrects the extended RAM (banked SRAM) issue. Installs by plugging into the U13 (74HC00) socket on the main board. Provides:

Fix: Replaces the Rev 1.0 NAND-based latch-enable logic with a NOR function (LOADL = NOR(SEL_L, WB), LOADH = NOR(SEH_L, WB)), preventing spurious latch pulses and making banked RAM work correctly with no firmware change
Interface: DIP-14 piggyback connector into U13 on the Rev 1.0 ACE Board

Firmware

This repository contains PlatformIO-based firmware for the ACE board.

AB Controller

Firmware/AB Controller/

Firmware for the ATmega1284P keyboard controller on the ACE board. Provides:

Dual keyboard input: PS/2 and 8×8 matrix keyboard simultaneously
PS/2 scancode to ASCII conversion
Matrix keyboard scanning with hardware debouncing
Modifier key support: Shift (symbols/punctuation) and Ctrl (control codes)
Buffered output via 65C22 VIA with CA1/CB1 data-ready strobes
Independent enable/disable for PS/2 and matrix inputs, releasing PORT A / PORT B so the 6502 can read the joysticks that share them
6502 reset control: drives RESB on PC7, holding the CPU in reset for ~250 ms at power-on, and debounces the reset button on PC0
Optional jiffy clock: pulses NMIB from the DS1511Y SQW input; compiled out unless ENABLE_SQW is defined

See Firmware/AB Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure bases and laser-cut top panels for the ACE system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for the ACE board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

ACE Board

Reference	Qty	Value	Description	DigiKey	Mouser	Other
BT1	1	CR2032	Battery Holder	BAT-HLD-001-THM-ND	712-BAT-HLD-001-THM
C1, C9–C30	23	100nF	Disc Capacitor	478-5732-ND		AMAZON
C2, C3, C5, C6, C8	5	1µF	Disc Capacitor	478-7667-ND		AMAZON
C4, C7	2	2.2nF	Disc Capacitor	478-SR151C222KAATR1CT-ND		AMAZON
C31	1	10uF	Electrolytic Capacitor 16v	P966-ND		AMAZON
D1	1	LED	3.0mm Power LED	732-5008-ND		AMAZON
D2, D3	2	BAT85	Schottky Diode	BAT85SCT-ND	78-BAT85S	AMAZON
J1	1	PHI2 SELECT	Pin Header 1×3 2.54mm			AMAZON
J2	1	CTS EN	Pin Header 1×3 2.54mm			AMAZON
J3	1	RESET SW	Pin Header 1×2 2.54mm			AMAZON
J4	1	DCD EN	Pin Header 1×3 2.54mm			AMAZON
J5	1	VDD	Pin Header 1×2 2.54mm			AMAZON
J6	1	JOYSTICK A	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J7	1	PADDLES	Pin Header 1×4 2.54mm			AMAZON
J8	1	JOYSTICK B	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J9	1	PORT B	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J10	1	PORT A	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J11	1	AUDIO L	RCA Jack	PJRAN1X1U02X-ND	502-PJRAN1X1U02X
J12	1	DB9 MALE (DTE)	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J13	1	PS/2	6-pin Mini-DIN		806-KMDGX-6S-BS	AMAZON
J14	1	KEYBOARD	Pin Header 1×16 2.00mm			AMAZON
J15	1	AUDIO R	RCA Jack	PJRAN1X1U03X-ND	502-PJRAN1X1U03X
J16	1	AUDIO	Pin Header 1×2 2.54mm			AMAZON
J17	1	5V DC	DC Barrel Jack	2073-DCJ200-10-A-K1-K-ND	640-DCJ200-10-A-K1-K
J18	1	CART	Card Edge 2×20 2.54mm	A31723-ND	571-5-5530843-4
J19	1	BUS	Box Header 2×20 2.54mm			AMAZON
J20	1	VCC	Pin Header 1×2 2.54mm			AMAZON
J21	1	POWER LED	Pin Header 1×2 2.54mm			AMAZON
J22	1	STORAGE	Pin Socket 2×10 2.54mm Horiz	S5563-ND
R1–R4, R25	5	10kΩ	1/8W Resistor	RNF18FTD10K0CT-ND		AMAZON
R5–R23, R26–R34	28	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND		AMAZON
R24	1	330Ω	1/8W Resistor			AMAZON
SW1–SW13, SW15, SW18–SW29, SW31, SW33–SW41, SW43, SW44, SW46–SW49, SW51–SW58, SW61, SW64–SW66	54	Various	Cherry MX Switch 1.00u	CH196-ND		AMAZON
SW59, SW60, SW63, SW67, SW68	5	CTRL / ALT / FN	Cherry MX Switch 1.25u	CH196-ND		AMAZON
SW16, SW30	2	TAB / Backslash	Cherry MX Switch 1.50u	CH196-ND		AMAZON
SW32	1	CAPS LOCK	Cherry MX Switch 1.75u	CH196-ND		AMAZON
SW14	1	BACKSPACE	Cherry MX Switch 2.00u	CH196-ND		AMAZON
SW42, SW45, SW50	3	SHIFT / ENTER	Cherry MX Switch 2.25u	CH196-ND		AMAZON
SW62	1	SPACE	Cherry MX Switch 6.25u	CH196-ND		AMAZON
SW17	1	RESET	Tact Push Button 6mm			AMAZON
SW69	1	POWER	SPDT Switch	EG4326-ND	612-400MSP1R6BLKM6QE
SW70	1	IO ENABLE	8× DIP Switch SPST			AMAZON
U1	1	W65C02S	65C02 CPU		955-W65C02S6TPG-14
U2	1	W65C22	65C22 VIA		955-W65C22N6TPG-14
U3	1	Pico9918A	VDP (VGA)			TINDIE
U4	1	65C51	ACIA			JAMECO
U5	1	74HC163	4-bit Counter	296-8246-5-ND	595-SN74HC163N
U6	1	ATmega1284-P	Keyboard Controller MCU	ATMEGA1284-PU-ND	556-ATMEGA1284-PU
U7	1	AS6C62256	32KB SRAM	1450-1033-ND	913-AS6C62256-55PCN
U8	1	AT28C256	32KB EEPROM	AT28C256-15PU-ND	556-AT28C25615PU
U9	1	6581	SID Chip			LINK
U10	1	MAX238xNG+	RS-232 Transceiver	MAX238CNG+-ND	700-MAX238CNG
U11–U14, U16	5	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U15	1	AS6C4008	512KB SRAM	1450-1027-ND	913-AS6C4008-55PCN
U17	1	74HC30	8-input NAND	296-9196-5-ND	595-CD74HC30E
U18	1	DS1511Y	RTC + NVRAM	DS1511Y+-ND	700-DS1511Y
U19, U20	2	74HC138	3-to-8 Decoder	296-1575-5-ND	595-SN74HC138N
U21, U22	2	74HC573	Octal Latch	296-12815-5-ND	595-CD74HC573EE4
U23	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N
X1	1	16MHz	DIP-14 Oscillator	X947-ND	815-ACO-16-EK
Y1	1	1.8432MHz	Crystal	3155-1.8432M20P2/49U-ND	815-AB-1.8432-B2

ACE CF Adapter

Reference	Qty	Value	Description	DigiKey	Other
D1	1	ACT LED	3.0mm LED	732-5008-ND	AMAZON
J1	1	STORAGE	Pin Header 2×10 2.54mm Horiz		AMAZON
J2	1	Compact Flash	CF Socket	4827-101D-TAAB-R01-ND
R1–R4	4	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND	AMAZON
R5	1	330Ω	1/8W Resistor		AMAZON

ACE RAM Patch

Reference	Qty	Value	Description	DigiKey	Mouser
J1	1	74HC00 (U13)	DIP-14 Piggyback Socket
U1	1	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U2	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License.

6502-ACE

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. Start with Your ACE, the tour of this board.

Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The ACE (All-in-one Computer Experience) is a complete, self-contained 65C02 computer on a single PCB. It integrates everything found across the COB's modular cards — CPU, memory, video, audio, storage, serial, GPIO, RTC, and keyboard controller — onto one board, delivering the full experience without a backplane or expansion cards.

Architecture

All AC6502 computers share:

CPU: 65C02 (or accurate emulation)
Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer (YOU ARE HERE)
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into `.prg` images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the ACE board.

ACE Board

Hardware/ACE Board/

The single integrated board hosting the W65C02S CPU and all peripherals. Provides:

CPU: W65C02S running at 1 or 2 MHz (jumper-selectable)
RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
ROM: 32KB EEPROM (28C256)
Video: Pico9918 (VGA 640×480)
Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
Storage: Storage adapter socket
Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
GPIO: 65C22 VIA (20 GPIO pins, 2× 16-bit timers, shift register)
RTC: DS1511Y real-time clock with battery-backed NVRAM
Keyboard Controller: ATmega1284P running AB Controller firmware
Input: PS/2 keyboard connector and 8×8 keyboard matrix header
Joystick: Two Atari 2600-compatible joystick ports (J6 JOYSTICK A on VIA PORT A, J8 JOYSTICK B on VIA PORT B), read as JOY(2) and JOY(1) respectively
Clock: 16 MHz DIP-14 full can oscillator (X1); drives the ATmega1284 at 16 MHz and the 65C02 at 1 or 2 MHz via the 74HC163 divider (J1 PHI2 SELECT jumper)
Reset: Manual reset button (SW17, just above Esc) connected to the ATmega1284, which also provides power-on reset to the 65C02
Power: 5V DC via barrel jack

Revision History

Rev 1.1

Fixes the gating of the LOADL and LOADH latch-enable signals for the 74HC573 latches (U21, U22) that drive the AS6C4008 banked SRAM. In Rev 1.0 the final two decode gates (U13C/U13D) were NANDs, which left the latches pulsing while idle and allowed spurious loads on reads, so the latches never reliably held a bank value.
The fix replaces the final NAND stage with a NOR function: LOADL = NOR(SEL_L, WB) and LOADH = NOR(SEH_L, WB), holding each latch enable low out of window and only pulsing on an in-window write. This makes banked RAM work correctly with no firmware change.
Implemented by adding one 74HC02 quad NOR (U23). The existing select logic in U13A/U13B is unchanged.
Some pull-up resistors changed from 1kΩ to 10kΩ: R1–R4 and R25 are now 10kΩ.
Added C31 (10µF electrolytic) at the power input for bulk decoupling capacitance.

Rev 1.0

Initial release.

ACE CF Adapter

Hardware/ACE CF Adapter/

A CompactFlash adapter board that connects to the Storage header on the ACE Board. Provides:

Interface: 8-bit IDE (True IDE) mode
Storage: CompactFlash socket. The BIOS filesystem divides the card into 256 disk banks of 1 MB each, so 256 MB is the usable capacity regardless of the card fitted

ACE RAM Patch

Hardware/ACE RAM Patch/

A piggyback patch board for Rev 1.0 of the ACE Board that corrects the extended RAM (banked SRAM) issue. Installs by plugging into the U13 (74HC00) socket on the main board. Provides:

Fix: Replaces the Rev 1.0 NAND-based latch-enable logic with a NOR function (LOADL = NOR(SEL_L, WB), LOADH = NOR(SEH_L, WB)), preventing spurious latch pulses and making banked RAM work correctly with no firmware change
Interface: DIP-14 piggyback connector into U13 on the Rev 1.0 ACE Board

Firmware

This repository contains PlatformIO-based firmware for the ACE board.

AB Controller

Firmware/AB Controller/

Firmware for the ATmega1284P keyboard controller on the ACE board. Provides:

Dual keyboard input: PS/2 and 8×8 matrix keyboard simultaneously
PS/2 scancode to ASCII conversion
Matrix keyboard scanning with hardware debouncing
Modifier key support: Shift (symbols/punctuation) and Ctrl (control codes)
Buffered output via 65C22 VIA with CA1/CB1 data-ready strobes
Independent enable/disable for PS/2 and matrix inputs, releasing PORT A / PORT B so the 6502 can read the joysticks that share them
6502 reset control: drives RESB on PC7, holding the CPU in reset for ~250 ms at power-on, and debounces the reset button on PC0
Optional jiffy clock: pulses NMIB from the DS1511Y SQW input; compiled out unless ENABLE_SQW is defined

See Firmware/AB Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure bases and laser-cut top panels for the ACE system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for the ACE board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

ACE Board

Reference	Qty	Value	Description	DigiKey	Mouser	Other
BT1	1	CR2032	Battery Holder	BAT-HLD-001-THM-ND	712-BAT-HLD-001-THM
C1, C9–C30	23	100nF	Disc Capacitor	478-5732-ND		AMAZON
C2, C3, C5, C6, C8	5	1µF	Disc Capacitor	478-7667-ND		AMAZON
C4, C7	2	2.2nF	Disc Capacitor	478-SR151C222KAATR1CT-ND		AMAZON
C31	1	10uF	Electrolytic Capacitor 16v	P966-ND		AMAZON
D1	1	LED	3.0mm Power LED	732-5008-ND		AMAZON
D2, D3	2	BAT85	Schottky Diode	BAT85SCT-ND	78-BAT85S	AMAZON
J1	1	PHI2 SELECT	Pin Header 1×3 2.54mm			AMAZON
J2	1	CTS EN	Pin Header 1×3 2.54mm			AMAZON
J3	1	RESET SW	Pin Header 1×2 2.54mm			AMAZON
J4	1	DCD EN	Pin Header 1×3 2.54mm			AMAZON
J5	1	VDD	Pin Header 1×2 2.54mm			AMAZON
J6	1	JOYSTICK A	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J7	1	PADDLES	Pin Header 1×4 2.54mm			AMAZON
J8	1	JOYSTICK B	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J9	1	PORT B	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J10	1	PORT A	Box Header 2×6 2.54mm	2057-BHR-12-VUA-ND		AMAZON
J11	1	AUDIO L	RCA Jack	PJRAN1X1U02X-ND	502-PJRAN1X1U02X
J12	1	DB9 MALE (DTE)	DB-9 Male	609-1481-ND	649-D09P33E4GX00LF
J13	1	PS/2	6-pin Mini-DIN		806-KMDGX-6S-BS	AMAZON
J14	1	KEYBOARD	Pin Header 1×16 2.00mm			AMAZON
J15	1	AUDIO R	RCA Jack	PJRAN1X1U03X-ND	502-PJRAN1X1U03X
J16	1	AUDIO	Pin Header 1×2 2.54mm			AMAZON
J17	1	5V DC	DC Barrel Jack	2073-DCJ200-10-A-K1-K-ND	640-DCJ200-10-A-K1-K
J18	1	CART	Card Edge 2×20 2.54mm	A31723-ND	571-5-5530843-4
J19	1	BUS	Box Header 2×20 2.54mm			AMAZON
J20	1	VCC	Pin Header 1×2 2.54mm			AMAZON
J21	1	POWER LED	Pin Header 1×2 2.54mm			AMAZON
J22	1	STORAGE	Pin Socket 2×10 2.54mm Horiz	S5563-ND
R1–R4, R25	5	10kΩ	1/8W Resistor	RNF18FTD10K0CT-ND		AMAZON
R5–R23, R26–R34	28	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND		AMAZON
R24	1	330Ω	1/8W Resistor			AMAZON
SW1–SW13, SW15, SW18–SW29, SW31, SW33–SW41, SW43, SW44, SW46–SW49, SW51–SW58, SW61, SW64–SW66	54	Various	Cherry MX Switch 1.00u	CH196-ND		AMAZON
SW59, SW60, SW63, SW67, SW68	5	CTRL / ALT / FN	Cherry MX Switch 1.25u	CH196-ND		AMAZON
SW16, SW30	2	TAB / Backslash	Cherry MX Switch 1.50u	CH196-ND		AMAZON
SW32	1	CAPS LOCK	Cherry MX Switch 1.75u	CH196-ND		AMAZON
SW14	1	BACKSPACE	Cherry MX Switch 2.00u	CH196-ND		AMAZON
SW42, SW45, SW50	3	SHIFT / ENTER	Cherry MX Switch 2.25u	CH196-ND		AMAZON
SW62	1	SPACE	Cherry MX Switch 6.25u	CH196-ND		AMAZON
SW17	1	RESET	Tact Push Button 6mm			AMAZON
SW69	1	POWER	SPDT Switch	EG4326-ND	612-400MSP1R6BLKM6QE
SW70	1	IO ENABLE	8× DIP Switch SPST			AMAZON
U1	1	W65C02S	65C02 CPU		955-W65C02S6TPG-14
U2	1	W65C22	65C22 VIA		955-W65C22N6TPG-14
U3	1	Pico9918A	VDP (VGA)			TINDIE
U4	1	65C51	ACIA			JAMECO
U5	1	74HC163	4-bit Counter	296-8246-5-ND	595-SN74HC163N
U6	1	ATmega1284-P	Keyboard Controller MCU	ATMEGA1284-PU-ND	556-ATMEGA1284-PU
U7	1	AS6C62256	32KB SRAM	1450-1033-ND	913-AS6C62256-55PCN
U8	1	AT28C256	32KB EEPROM	AT28C256-15PU-ND	556-AT28C25615PU
U9	1	6581	SID Chip			LINK
U10	1	MAX238xNG+	RS-232 Transceiver	MAX238CNG+-ND	700-MAX238CNG
U11–U14, U16	5	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U15	1	AS6C4008	512KB SRAM	1450-1027-ND	913-AS6C4008-55PCN
U17	1	74HC30	8-input NAND	296-9196-5-ND	595-CD74HC30E
U18	1	DS1511Y	RTC + NVRAM	DS1511Y+-ND	700-DS1511Y
U19, U20	2	74HC138	3-to-8 Decoder	296-1575-5-ND	595-SN74HC138N
U21, U22	2	74HC573	Octal Latch	296-12815-5-ND	595-CD74HC573EE4
U23	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N
X1	1	16MHz	DIP-14 Oscillator	X947-ND	815-ACO-16-EK
Y1	1	1.8432MHz	Crystal	3155-1.8432M20P2/49U-ND	815-AB-1.8432-B2

ACE CF Adapter

Reference	Qty	Value	Description	DigiKey	Other
D1	1	ACT LED	3.0mm LED	732-5008-ND	AMAZON
J1	1	STORAGE	Pin Header 2×10 2.54mm Horiz		AMAZON
J2	1	Compact Flash	CF Socket	4827-101D-TAAB-R01-ND
R1–R4	4	1kΩ	1/8W Resistor	RNF18FTD1K00CT-ND	AMAZON
R5	1	330Ω	1/8W Resistor		AMAZON

ACE RAM Patch

Reference	Qty	Value	Description	DigiKey	Mouser
J1	1	74HC00 (U13)	DIP-14 Piggyback Socket
U1	1	74HC00	Quad NAND	296-1563-5-ND	595-SN74HC00N
U2	1	74HC02	Quad NOR	296-1565-5-ND	595-SN74HC02N

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License.

Name		Name	Last commit message	Last commit date
CAD		CAD
Firmware/AB Controller		Firmware/AB Controller
Hardware		Hardware
Images		Images
Libraries		Libraries
Models		Models
Production		Production
Schematics		Schematics
.gitignore		.gitignore
LICENSE		LICENSE
README.md		README.md

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6502-ACE

Table of Contents

Overview

Architecture

Systems

Software

Hardware

ACE Board

Revision History

ACE CF Adapter

ACE RAM Patch

Firmware

AB Controller

CAD

Production

Schematics

Libraries

Bill of Materials

ACE Board

ACE CF Adapter

ACE RAM Patch

License

About

Resources

Stars

Watchers

Forks

Contributors

Languages

Latest commit

History

Folders and files

Repository files navigation

6502-ACE

Table of Contents

Overview

Architecture

Systems

Software

Hardware

ACE Board

Revision History

ACE CF Adapter