Using AI to Build Commodore 64 Games and Cartridge Tools

Summary

This long-form account describes how the author used Anthropic’s Claude and Google’s Gemini to create and improve Commodore 64 cartridge software and related tools. The initial goal was to convert IDE64 versions of Portal and Alter Ego into EasyFlash cartridges, without source code, by locating and rewriting calls in compiled binaries. Claude eventually wrote its own disassembler and learned to control the VICE emulator after existing MCP documentation proved incomplete, producing playable read-only cartridges, although they initially lacked game saving. The author then explored EasyFlash persistence, whose zero-only writes and block-erasure behavior require a two-block “ping pong” storage design, making frequent saves difficult. A similar conversion of Wasteland proved harder because the game stores persistent world changes in its large binary data, and an SD2IEC-based approach was not yet bootable. Claude also enhanced a VICE snapshot-to-PRG converter, adding or improving MagicDesk support, memory detection, loader placement, and related user-interface changes. When Anthropic credits ran out, the author gave Gemini Claude’s documented knowledge and found that Gemini could continue the work, including capturing Kernel LOAD and SAVE operations on EasyFlash. The agents integrated the EAFS file-system library, while support for games that write high scores through file operations remained untested. By late June 2026, tested LOAD and SAVE vector capture was available, but increased memory requirements meant many automatic conversions would fail unless suitable memory remained available. The author released three early cartridges, code, and a knowledge pack containing documentation and tools, and invited the community to test the results, inspect the code, and reuse the accumulated AI guidance. The article presents AI as a way to make otherwise unavailable C64 preservation work feasible within limited personal time, while acknowledging incomplete features and the need for community feedback.