For those too young to remember, the 6502 powered computers such as the Apple //, the Atari 400/800, and various Commodore models like the PET-2001 and the C-64. An introduction to 6502 programming can be found at Machine Language For Beginners

Orgasm 0.22 for OS X

This is an OS X version of Robert Norris' 6502 assembler called Orgasm. It can be used to generate object files for use with j6502. You can download it at

To run it, type orgasm -o output-file input-file, where input-file is a 6502 assembler file, and output-file is the generated object code.

j6502 1.2

This is a new version of Richard Russo's 6502 simulator called j6502. The documentation still refers to version 1.0, but the program should be comprehensible as it is. You can download it at

Changes from the original version include:

  • added About dialog
  • moved CPU commands into separate menu
  • replaced popup menus with UI elements
  • the file chooser now remembers the most recently used directory
  • implemented breakpoints
  • added Run command, which steps until it hits a BRK instruction, a bad opcode or a breakpoint.
  • The codebase has been moved into the Java 5 era (typesafe data structures, removal of obsolete methods, etc.)