What CHIP-8 Is

CHIP-8 is an interpreted virtual machine designed in 1977 for hobby computers (RCA COSMAC VIP). It became famous as the simplest possible VM: 35 instructions, 4 KiB RAM, 16 registers, 64x32 monochrome display.

Why emulate it?

• Smallest possible VM: ~500 LOC of Python or C.
• Excellent first emulator project: shorter than NES, simpler than Game Boy.
• Public domain ROMs: Pong, Tetris, Space Invaders.
• Bridge to bigger emulators: same patterns scale to NES, Game Boy.

Specs:

• CPU: custom interpreter, no real chip.
• RAM: 4096 bytes (0x000-0xFFF).
  • 0x000-0x1FF: reserved for interpreter (font set lives here).
  • 0x200-0xFFF: program ROM + work RAM.
• Registers: 16 8-bit (V0-VF). VF is flag/carry.
• Index register I: 12-bit (memory address).
• PC: 12-bit, starts at 0x200.
• Stack: 16 levels of return addresses.
• Sound timer: 8-bit, 60 Hz. Beeps if non-zero.
• Delay timer: 8-bit, 60 Hz.
• Display: 64x32 monochrome bitmap.
• Input: 16-key hex keypad.

Frequency:

• ~500 instructions per second (variable).
• Timers tick at 60 Hz.
• Display refresh at 60 Hz.

Each instruction is 2 bytes (big-endian). 35 unique opcodes. Easy to decode.

Real implementations:

• Octo (web-based, Tom Wickline): runs ROMs + has IDE.
• mGBA (handheld emulator): supports CHIP-8.
• Many hobby projects in every language.

Modern variants:

• SuperChip (1991): adds 64x64 hi-res mode + more keys.
• XO-Chip (2014): 16 colors, audio, big memory.

For our build: classic CHIP-8 only. Simple + complete.

Reference: Cowgod's CHIP-8 Technical Reference (the canonical doc).