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Minimal Intel 8086 emulator written in Common Lisp
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cl8086 - a proof-of-concept Intel 8086 emulator written in Common Lisp

This is a basic Intel 8086 emulator, which has enough functionality to execute the "codegolf" program (

Please use the "codegolf" branch to run the executable. master is not guaranteed to remain compatible with that program's non-standard assumptions, and it will likely break at some point.

Though I wrote the code from scratch, I did use Julien Aubert's Python emulator implementation ( as a rough guide and a source of inspiration, as well as a template for this documentation.

My code is licensed under the MIT License. The "codegolf" program has an unknown license.

Instruction Support

This was designed to support only the bare minimum required to run the aforementioned program "codegolf". I have since started to further extend it.

Currently supported

  • All 8086 instructions not involving stuff listed as possible future additions
  • All 8 general purpose byte and word registers
  • IP register
  • Flags: AF, CF, DF, OF, PF, SF, ZF (also FLAGS register)
  • Loading instructions via a vector
  • Binary-coded decimal (both packed and unpacked)
  • String functions
  • rep- and loop-type prefixes
  • Segment registers that can be manipulated
  • Opcode prefixes for segment overrides
  • Full 1 MB RAM vector
  • Interrupts
  • Port-mapped IO

Probably won't be supported later

  • Floating-point operations
  • LOCK assertions
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