CHIP-8

CHIP-8 is an interpreted programming language developed in the mid-1970s by Joseph Weisbecker for the COSMAC VIP and Telmac 1800 microcomputers. It was designed to make game programming easier. Programs are run on a virtual machine with a 64×32 pixel monochrome display, 16 input keys, and a simple sound timer.

SuperChip extends CHIP-8 with a 128×64 high-resolution mode, 16×16 sprites, scrolling, persistent flag registers, and a larger font. Select "SuperChip (Legacy)" for original HP-48 behavior or "SuperChip (Modern)" for updated quirks.

XO-CHIP extends SuperChip (Modern) with 4-color graphics via two bitplanes, 64KB addressable memory, ranged register load/save, 16 flag registers, scroll-up, and programmable audio with a 16-byte pattern buffer and variable pitch control. Use the Octo/CGA/LCD color themes for best results with XO-CHIP 4-color ROMs.

XO-CHIP Memory Quirks:

• 64KB Address Space: Expands from 4KB to 65,536 bytes. The F000 NNNN double instruction loads a full 16-bit address into I (PC advances by 4 bytes instead of 2).
• Fx55/Fx65 — I Unchanged: XO-CHIP hard-codes the S-CHIP behavior where the Index register (I) is not incremented after load/store operations. Original COSMAC VIP incremented I by x+1.
• 5XY2/5XY3 — Arbitrary Range Save/Load: Saves or loads an inclusive range of registers Vx through Vy, bypassing the V0 dependency of Fx55/Fx65. For example, 5482 dumps V4–V8 without touching V0–V3. I remains unmodified.
• F002 — Audio Pattern Buffer: Copies 16 bytes from memory at I into a dedicated sound buffer. The bytes at I must contain valid pattern data before execution, and care is needed to avoid collision with active variable storage.

Keyboard mapping: 1234 / QWER / ASDF / ZXCV → CHIP-8 keys 123C / 456D / 789E / A0BF

Quirks by mode:

• CHIP-8: VF reset ✓, Memory increment ✓, Display wait ✓, Shift from VY, Jump V0+NNN
• S-CHIP Legacy: No VF reset, No memory increment, Display wait ✓, Shift from VX, Jump VX+XNN
• S-CHIP Modern: No VF reset, No memory increment, No display wait, Shift from VX, Jump VX+XNN
• XO-CHIP: Modern S-CHIP base + No I increment (Fx55/Fx65), 64KB memory (F000 NNNN), 2 bitplanes (4 colors), plane N, 5XY2/5XY3 ranged save/load, F002 audio pattern buffer, pitch register, scroll-up, 16 flag registers