Opcodes

Carry around decades of retro computer knowledge in your pocket and on your wrist. Instruction sets, architecture notes, programmer tools, games, and lots more.

Opcodes – The Retro CPU Reference

The definitive opcode reference for the legendary processors that launched the personal computer revolution.

Whether you're a retrocomputing enthusiast, a student of computer history, writing code for classic hardware, or just a big old nerd - the Opcodes app gives you everything you need.

Eighteen iconic processors covered: Intel 4004 · Intel 8008 · Intel 8080 · Intel 8085 · Intel 8088 · Zilog Z80 · Motorola 6800 · Intel 8085 · Motorola 6809 · MOS 6502 · Signetics 2650 · RCA 1802 - SC/MP · Motorola 68000 · Intel 8086 · WDC 65816 · Texas Instruments TMS9900 · INMOS Transputer · ARM2

For every opcode: 

• Full description of what the instruction does. • Hex, octal, and decimal values. • Flags affected. • Addressing modes and cycle counts. • Assembly code examples - including loops, conditionals, and common patterns.

More than just opcodes: 

• CPU history and historical context. • IC pinout diagrams. • Notable systems that used each chip, with memory maps. • Chip variants and successors. • A silly card game(!) • Simple assembler / disassembler for many CPUs.

Built for exploration: 

• Search for opcodes by name or category. • Sort by mnemonic, opcode byte, or category. • Filter by category, Quick Find with a colorful map. • Undocumented instructions clearly marked and optionally displayed.

More than microprocessors: 

• Information on key support chips: video, sound, memory and more.

Beautifully designed: 

• Clean, readable layout optimised for quick reference. • Multiple colour themes. • Full "dark mode" support.

Everything is included with absolutely no in-app purchase required.

What's New in 1.6

• Quiz game - test your CPU knowledge! • Share CPU cards - beautiful shareable images showing specs and history for any processor • External references - curated links to community resources for all 18 CPUs • "Opcodes display first" setting - choose whether selecting a CPU shows opcodes or info first • Chip-maker colour themes - Zilog, MOS Tech, and Motorola replace the old themes • Enhanced 6502 docs - JMP page boundary bug, BRK behaviour, and Read-Modify-Write quirks • Fixed Scratchpad hang when switching tabs