Opcodes

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, or writing code for classic hardware, Opcodes gives you everything you need - right in your hand.

Twelve iconic processors covered: Intel 4004 · Intel 8008 · Intel 8080 · Intel 8085 · Intel 8088 · Zilog Z80 · Motorola 6800 · Motorola 6809 · MOS 6502 · Signetics 2650 · RCA 1802 - SC/MP

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

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

Beautifully designed: 

• Clean, readable layout optimised for quick reference 
• Multiple colour themes 
• Full Dark Mode support

From the 4-bit 4004 - the chip that started it all - to the Z80 powering countless home computers of the 1980s, Opcodes is the reference library you'll keep coming back to (if you're a bit of a nerd - no judgement!)