DEC Opcodes

About this app

Dec Opcodes – DEC Architecture Reference Before the microprocessor, there was DEC. The minicomputers built by Digital Equipment Corporation didn't just advance computing - they defined it. Unix was born on a PDP-7. Spacewar! ran on a PDP-1. The field of Artificial Intelligence was born on the PDP-10. The VAX powered universities and research labs worldwide for a generation. DecOpcodes puts the complete instruction sets of these legendary machines in your pocket. Five iconic architectures covered: PDP-1 (1960) · PDP-8 (1965) · PDP-10 (1966) · PDP-11 (1970) · VAX (1977) For every instruction:  • Full description of what the instruction does  • Octal and hex encoding  • Flags affected  • Addressing modes, word count, and cycle counts  • Assembly code examples and implementation notes But there is a lot more than just dry opcodes:  • Complete system specifications and register architecture  • Historical context and cultural impact  • Archival photographs - front panels, system cabinets, and more  • Notable installations and the systems they powered  • Architecture variants and successors • Interactive lessons on assembly language and console operations (ideal if you have an PiDP emulator) Built for exploration:  • Search across all systems instantly • A simple assembler for PDP-1, -8 and -11 code • Filter by instruction category  • Sort alphabetically or by category • Favorite instructions for quick reference Beautifully designed:  • System-specific accent colours  • Five themes including Terminal green and Blinkenlights orange  • Full Dark Mode support From the 18-bit simplicity of the PDP-1 to the 32-bit sophistication of the VAX, DecOpcodes is a fascinating and interactive journey through the machines that made modern computing possible. All features are free and unlocked. If you like the app you can always leave a nice review or tip the developer!

What's New in v1.9 • DEC Glossary - Searchable guide to 45+ terms across buses, memory, storage, I/O, processors, software, and DEC culture • PDP-11 instructions added - MFPI, MFPD, MTPI, MTPD (previous-space memory access) and SPL (set priority level) • Memory Maps corrected - Separate PDP-11/45 (256KB) and PDP-11/70 (4MB) layouts; KW11-L and KW11-P clocks added to I/O page; byte units for PDP-11 and VAX • Official DEC handbooks linked - Architecture Handbook PDFs from bitsavers for all five systems in Programming Resources • System landing page setting - Choose whether tapping a system opens the instruction list or the system info page • PiDP-8 Quick Start expanded - OS/8 first commands, paper tape bootstrap sequence, Spacewar! controls, TSS/8 multi-user login, USB storage guide • PDP-1 toggle programs fixed - Correct memory addresses and proper ADD-based counting loop • Dynamic Type support - All sidebar and card text now scales with your preferred font size • Accessibility improved - Better VoiceOver labels and touch targets throughout • Faster launch - Removed artificial splash screen delay

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1. First observed Aug 22, 2026 · 2:42 PM Free