# Opcodes - retro CPU reference — Decades of nerd knowledge > Retro CPU opcode reference with historical context and assembly examples. (iPhone/iPad app by John Kennedy.) - Source: https://appshunter.io/ios/app/opcodes-retro-cpu-reference/id6760205834 (this page in markdown: same URL + `.md`) - Developer: [John Kennedy](https://appshunter.io/developer/284943103) - Category: Education - Price: Free with in-app purchases - Rating: 4.80/5 from 6 App Store ratings - Age rating: 4+ - Requires: iOS 18.0 · 58 MB - Languages: American English - Released: 2026-03-17 - Data updated: 2026-09-06 - Monetization: free - User reviews in markdown: https://appshunter.io/ios/app/opcodes-retro-cpu-reference/id6760205834/reviews.md ## What is 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, 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 ## Key features - Opcode reference for 18 iconic processors - Detailed instruction descriptions - Hex, octal, decimal values - Flags affected, addressing modes, cycle counts - Assembly code examples - CPU history and pinout diagrams - Simple assembler/disassembler ## Pricing and in-app purchases Base price: Free. **One-time purchases** | Purchase | Price | Type | | --- | --- | --- | | Buy Me a Coffee | $0.99 | one-time | ## Frequently asked questions about Opcodes ### What processors does Opcodes cover? Opcodes covers eighteen iconic processors, including the Intel 4004, 8080, 8085, 8088, Zilog Z80, Motorola 6800, 6809, MOS 6502, and ARM2, among others. This extensive list ensures comprehensive coverage for retrocomputing enthusiasts. ### What kind of information is provided for each opcode? For every opcode, Opcodes provides a full description of the instruction's function, its hex, octal, and decimal values, the flags it affects, addressing modes, and cycle counts. It also includes assembly code examples for common patterns and logic. ### Does Opcodes offer any historical context beyond just opcodes? Yes, Opcodes goes beyond just opcodes by including CPU history and historical context, IC pinout diagrams, notable systems that used each chip with memory maps, and information on chip variants and successors. It also features a card game and a simple assembler/disassembler. ### How can I find specific opcodes or information within Opcodes? Opcodes is built for exploration with features like searching for opcodes by name or category, sorting by mnemonic, opcode byte, or category, and filtering by category. A colorful Quick Find map is also available for easy navigation. ### Is Opcodes available on multiple devices? Yes, Opcodes is supported on both iPhone and iPad, making it accessible to a wide range of users interested in retro computing. The clean design is optimized for quick reference on these devices. ### How often is Opcodes updated? The latest version of Opcodes is 1.6.1, and it was last updated on June 2, 2026. This indicates a commitment to maintaining and improving the reference material. ### What is the age rating for Opcodes? Opcodes has an age rating of 4+, making it suitable for a broad audience interested in learning about computer history. The app's educational content is accessible to younger users as well. ### Does Opcodes have ads? No, Opcodes does not contain advertisements. The app is completely free to use and includes all its features without any in-app purchases or ad interruptions. ## Version history (last 5 releases) ### 1.12 — 2026-08-24 Improved display of flags, and source/destination order Improved Motorola 680x0 instruction display Added SP0256 to support chips, complete with working allophone system. Try making say rude words! ### 1.11 — 2026-07-28 Updated transputer instruction list. Some more information on Z80N. ### 1.10 — 2026-07-25 Z80N instructions for Spectrum Next developers ### 1.9 — 2026-07-22 Bug fixes. New compact opcode reference chart option. ### 1.8 — 2026-07-13 What's New • Complete Motorola 680x0 family added: 68010, 68020, 68030, 68040, and 68060 • Includes FPU instructions (68881/68882 coprocessor) with the 68020 • Includes MMU instructions (PFLUSH, PTEST, PMOVE) with the 68030 • Cache control instructions (CINV, CPUSH, MOVE16) with the 68040 • Detailed historical notes tracing the architecture from 68,000 to 2.5 million transistors • CPU Quiz now accessible from iPad sidebar • Improved accessibility: answer feedback icons for color-blind users • Larger tap targets on detail view buttons • VoiceOver labels added to cross-reference navigation • Fixed incorrect IBM PC XT data attribution under 8086 • Removed unused font asset ## More apps by John Kennedy - [Pocket Universe](https://appshunter.io/ios/app/pocket-universe/id306916838) - [What's Up?](https://appshunter.io/ios/app/whats-up/id393023070) - [Sky Time](https://appshunter.io/ios/app/sky-time/id473539346) - [Spelling Test](https://appshunter.io/ios/app/spelling-test/id478561217) - [Asstrology - Your Future Is Behind You](https://appshunter.io/ios/app/asstrology-your-future-is-behind-you/id486930635) - [Pocket Universe Classic](https://appshunter.io/ios/app/pocket-universe-classic/id567184849) All apps by John Kennedy: https://appshunter.io/developer/284943103 ## Related topics [opcodes](https://appshunter.io/ios/topics/opcodes) · [dec opcodes](https://appshunter.io/ios/topics/dec-opcodes) · [z80 reference](https://appshunter.io/ios/topics/z80-reference) --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-06.*