Opcodes - retro CPU reference
Opcodes - retro CPU reference is made and published by John Kennedy. AppBrain is an independent app data site and isn't affiliated with John Kennedy. The app name, icon, screenshots and description belong to John Kennedy and are shown as published on the App Store.
AppBrain's verdict
- Rating on App Store
- 4.83
- 6 ratings
- Last updated
- August 24, 2026
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Releases
Updates seen on the App Store- Version
- 1.12
- Launched
- March 2026
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Technology
Found in the app by AppBrain- Price
- Free
- App size
- 58.3 MB
- Content rating
- Everyone
Technologies used by Opcodes - retro CPU reference
About the app and developer
About Opcodes - retro CPU reference
Opcodes - retro CPU reference is an education app developed by John Kennedy.
What is the rating of Opcodes - retro CPU reference?
Opcodes - retro CPU reference is rated 4.83 out of 5 stars, based on 6 ratings.
Is Opcodes - retro CPU reference free?
Opcodes - retro CPU reference is free. The app size is 58.28 MB. The latest version available is 1.12. The last update was on August 24, 2026.
What are the requirements for Opcodes - retro CPU reference?
The app has a content rating of Everyone. The app has been available on the App Store since March 2026.
Developer information for John Kennedy
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Store listing
By John Kennedy, from the App Store
Description by John Kennedy Written by the developer, not by AppBrain. Click to read.
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 CPU, with memory maps and other background information.
• 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.
Cool design:
• Clean, readable layout optimised for quick reference.
• Multiple colour themes.
• Full "dark mode" support.
Everything is included with absolutely no in-app purchase required.
Recent additions:
• 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