Opcodes

Retro CPU reference

Free · In‑App Purchases · Designed for iPad. Not verified for macOS.

How many bits do you need? 4? 8? 16? Sounds good! 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. Sixteen 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 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.

Ratings & Reviews

  • 5.0
    out of 5
    2 Ratings

Updated the navigation with an old-school carousel view. Added ASCII/PETSCII table of characters. Added information on 25 of the most popular support chips (covering sound, I/O, video, and memory).

Version 1.4

The developer, John Kennedy, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Not Collected

    The developer does not collect any data from this app.

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    Information

    Seller
    • John Kennedy
    Size
    • 39.4 MB
    Category
    • Education
    Compatibility
    Requires iOS 18.0 or later.
    • iPhone
      Requires iOS 18.0 or later.
    • iPad
      Requires iPadOS 18.0 or later.
    • Mac
      Requires macOS 15.0 or later and a Mac with Apple M1 chip or later.
    • Apple Vision
      Requires visionOS 2.0 or later.
    Languages
    • English
    Age Rating
    4+
    In-App Purchases
    Yes
    Copyright
    • © John Kennedy 2026
  • Developer Website
  • Privacy Policy

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