6502-ACE

A.C. Wright 6502
All-in-One Computer Experience

This is your ACE

One board, one computer, everything on it — including the keyboard. The 6502-ACE folds every function of the modular COB's card stack onto a single PCB: processor, memory, video, sound, storage, serial, clock, joysticks, and 67 mechanical keys soldered straight to the board. Nothing to fit, nothing to decide. Switch it on and start typing. It is the finished machine of the AC6502 family, built around the Western Design Center W65C02S — the fully-static CMOS descendant of the 1975 MOS 6502.

What is on the board

CPU	WDC W65C02S at 1 MHz, jumper-selectable to 2 MHz
RAM	32 KB SRAM (62256) + 512 KB banked SRAM (AS6C4008)
ROM	32 KB EEPROM (28C256) — the whole 6502 BIOS
Video	Pico9918 — TMS9918A-compatible, VGA out, 40×24 text, 16 colors
Sound	ARMSID — MOS 6581 replacement, 3 voices, RCA out
Storage	CompactFlash on the ACE CF Adapter (8-bit True IDE)
Serial	65C51 ACIA + MAX238, DB-9, 19200 8-N-1
GPIO	65C22 VIA — two 8-bit ports and two timers
Clock	DS1511Y, battery-backed, with 256 bytes of NVRAM
Keyboard	67 Cherry MX switches on the board, plus PS/2 (ATmega1284P, AB Controller)
Sticks	Two Atari 2600-compatible joystick ports
Power	5 V DC, 2–3 A, barrel jack

Two switches and a jumper

The power switch is the cold start. The small white reset button, just above ESC, is the warm one: it restarts the machine but leaves memory alone, so your program and variables are still there afterwards. That makes it the safe way out of anything that has run away.

PHI2 SELECT picks 1 or 2 MHz. The eight-way IO ENABLE DIP bank has one switch per I/O section — leave them all on; they are for fault-finding.

Memory map

Range	Contents
$0000–$07FF	Zero page, stack, Kernal and BASIC buffers
$0800–$7FFF	Your program, variables and strings (30 KB)
$8000–$9FFF	I/O — eight 1 KB device slots
$A000–$B7FF	Kernal + jump table
$B800–$BFFF	Character set
$C000–$EDFF	BASIC interpreter
$EE00–$FEFF	Machine-code Monitor
$FF00–$FFF9	Wozmon
$FFFA–$FFFF	NMI, RESET and IRQ vectors

Did you know?

The entire operating system — Kernal, machine-code Monitor and a full BASIC — fits in one 32 KB EEPROM, with room to spare for the character set.

The Pico9918 is a Raspberry Pi Pico pretending, cycle for cycle, to be the 1979 TMS9918A from the ColecoVision and the MSX.

Three version numbers ship in that one chip: BIOS v1.5, BASIC V2.0 and Monitor v1.1.

6502-ACE

A.C. Wright 6502
All-in-One Computer Experience

Switching on

The splash appears, counts down five seconds and boots BASIC. You get a banner, a byte count, and the prompt — which is OK. Everything is typed there.

-- 6502 BIOS v1.5 --

6502 BASIC V2.0
 30718 BYTES FREE

OK

Press ENTER during the countdown to skip it, or ESC to boot the machine-code Monitor instead. Type X there to come back. BASIC and the Monitor have sheets of their own, and the whole guide is at acwright.github.io/6502-DOCS.

First things to type

Type this	What happens
PRINT "HELLO"	Puts text on the screen
PRINT 6502*2	Use it as a calculator — answers `13004`
LIST	Show the program in memory
RUN	Run it
NEW	Throw it away and start again
MEM	Free bytes, what the machine found, and the current disk

Loading and saving

Command	What happens
DIR	List the files on the CompactFlash card
LOAD "NAME"	Load a program
SAVE "NAME"	Save the one you have
DEL "NAME"	Delete a file
DISK 3	Switch to disk bank 3. The card holds 256 of them, 16 files each

Fun to try — no card needed

Endless name scroll — type
10 PRINT "ACE ";
20 GOTO 10
then RUN. Press ESC to stop it.

Random maze —
10 PRINT CHR$(47 + 45 * INT(RND(1) * 2));
20 GOTO 10
fills the screen with slashes that read as a maze.

Make some noise — VOL 15 then SOUND 1,440,50 plays a concert A for half a second. Voices are 1 to 3; volume 0 to 15.

Wiggle a joystick — PRINT JOY(1) reads 255 with nothing held, and drops a bit for each direction you push.

Wozmon easter egg — SYS 65280 lands you in a copy of the original Apple I monitor. Its prompt is a backslash; FF00.FF07 reads eight bytes. Press the reset button to come back.

BASIC in one table

Statement	Purpose
PRINT	Show text or numbers
INPUT A	Ask the person at the keyboard for a value
LET A=5	Give a variable a value (`LET` optional)
IF…THEN	Make a decision
FOR…NEXT	Counting loop — one `NEXT` per loop
GOTO / GOSUB	Jump to, or call, a line number
CLS / LOCATE / COLOR	Clear the screen, move the cursor, set the colors
PEEK / POKE	Read or write one byte of memory
SYS addr	Call machine code and come back

Handy keys

Key	Does
ESC	Stops a running program. The one to remember
Ctrl + C	The same thing, if that is the habit you have
Backspace	Rub out the last character
Reset button	Warm restart — your program survives