c64

name

c64

description

Orientation and router for Commodore 64 programming and hardware — the architecture at a glance, the memory/IO map, and a "which skill answers this" index across the focused c64-* skills (BASIC, graphics, sprites, VIC-II, SID, 6510 assembly, KERNAL, memory map, CIA, I/O, disk, tape, game ports, PETSCII, keyboard, hardware, disassembly). Use this skill WHEN a C64 question is broad, vague, or cross-cutting ("how does the C64 work", "where do I start", "what chip does sound"), when you need the high-level memory map or chip locations, or to route a specific question to the right c64-* skill. For depth, defer to the specific sibling skill.

Commodore 64 — overview & router

The C64 (1982, ~17M sold) is a 6510-based 8-bit home computer: 64 KB RAM, a VIC-II video chip, a SID sound chip, two CIA I/O chips, and BASIC + KERNAL in ROM. This skill is the map of the territory and a router to the focused c64-* skills. Use it to orient, then open the specific skill for depth.

The machine in one screen

Part	Chip	Job	Lives at	Skill
CPU	6510 (6502 + I/O port)	runs code; $00/$01 bank ROM/RAM	—	c64-assembly
Video	VIC-II 6567(NTSC)/6569(PAL)	screen, sprites, raster, IRQ	$D000-$D3FF	c64-vic-ii, c64-graphics, c64-sprites
Sound	SID 6581	3-voice synth + filter	$D400-$D7FF	c64-sid
I/O #1	CIA1 6526	keyboard, joysticks, timer IRQ	$DC00-$DCFF	c64-cia, c64-keyboard, c64-game-ports
I/O #2	CIA2 6526	serial bus, user port, VIC bank, NMI	$DD00-$DDFF	c64-cia, c64-io
Banking	PLA 82S100	decodes ROM/RAM/IO/charROM	—	c64-memory-map, c64-hardware
Firmware	BASIC + KERNAL ROM	language + OS routines	$A000,$E000	c64-basic, c64-kernal

Memory map at a glance

$0000-$00FF  zero page    ($00/$01 = 6510 bank-switch port)
$0100-$01FF  CPU stack
$0200-$03FF  OS work area + buffers (IRQ vector $0314, tape buffer $033C)
$0400-$07FF  default screen RAM (sprite pointers $07F8-$07FF)
$0800-$9FFF  BASIC program / free RAM   (BASIC starts $0801)
$A000-$BFFF  BASIC ROM      (or RAM, switchable)
$C000-$CFFF  free RAM (4K) — favourite spot for ML
$D000-$DFFF  I/O: VIC $D000 / SID $D400 / colorRAM $D800 / CIA1 $DC00 / CIA2 $DD00
             (or character ROM, or RAM — depends on $01)
$E000-$FFFF  KERNAL ROM     (or RAM); jump table $FF81-$FFF3

Full detail, the $01 banking-bit table, and the PLA logic → c64-memory-map.

Which skill answers this?

You want to…	Skill
write/understand BASIC; a keyword's syntax	c64-basic
print special chars, color/cursor codes, build a text UI	c64-petscii
know what a key does (C=, RUN/STOP, RESTORE), use the editor	c64-keyboard
draw chars/bitmaps, set screen colors, scroll, custom fonts	c64-graphics
make/move/collide sprites	c64-sprites
exact raster timing, bad lines, all video modes, demo effects	c64-vic-ii
produce sound/music, program the SID	c64-sid
write 6510 machine language; call ML from BASIC	c64-assembly
call OS routines (print, load, save, input)	c64-kernal
the full memory map / banking / where things live	c64-memory-map
timers, IRQ/NMI, the chip behind keyboard/joystick/serial	c64-cia
files & devices, serial bus, printer, modem, RS-232, user/cartridge port	c64-io
disk drive: load, save, directory, DOS commands	c64-disk
cassette / Datasette load, save, "directory"	c64-tape
read joysticks, paddles, light pen	c64-game-ports
repair, pinouts, voltages, board revisions, chips	c64-hardware
reverse-engineer a .prg / dump / listing	c64-disassembly

Quick answers to common questions

• Which control port is "player 1"? Hardware: port 1 reads at CIA1 $DC01, port 2 at $DC00. By software convention most single-joystick games use control port 2. Detail → c64-game-ports.
• What does the C= (Commodore) key do? With SHIFT it toggles the upper-case/graphics vs upper/lower-case character set; held with a number key it selects one of the second set of text colors; it can also slow listings. → c64-keyboard.
• How do I see a disk directory? LOAD"$",8 then LIST. → c64-disk.
• How do I list a tape "directory"? Tape is sequential — there is no random-access directory; you search forward for files. → c64-tape.
• How do I clear the screen / where is screen RAM? PRINT CHR$(147) (or POKE screen codes to $0400-$07FF, colors to $D800). → c64-petscii, c64-graphics.
• Where do I put a machine-language routine? $C000 (free 4K) or the tape buffer $033C; call with SYS. → c64-assembly.
• PAL vs NTSC? PAL = 6569 (50 Hz, 63 cycles/line, 312 lines); NTSC = 6567 (60 Hz, ~64–65 cycles/line, 262/263 lines). Matters for timing/music. → c64-vic-ii.

How to use the set

Each c64-* skill is self-contained and carries the relevant sliced reference docs under its own references/. Start here for orientation or a one-liner; jump to the specific skill for register layouts, code, and exact behavior. For generic 6502/65C02/65816 CPU semantics beyond the C64's 6510, the optional companion repo https://github.com/sunsided/6502-skills pairs well — not required.