David Given has revealed that he has ported Digital Research’s CP/M operating system to the 6502 microprocessor. This classic operating system was originally released in 1977 and was designed for use with the 8080 and Z80 microprocessors. Currently the port is still in beta, however the initial release is available to the general public.
Given’s port of CP/M supports relocatable binaries, which means that unmodified binaries can run on any system. This is necessary because 6502 systems tend to be much less standardized than 8080 and Z80 systems. Currently, the port runs on a variety of systems including the BBC Micro, BBC Master, BBC Tube, Electron, Commodore 64, Commander X16, and the Apple IIe.
On the BBC Micro in mode 7, the port provides a 21kB transient program area (TPA), while on the Master, it offers approximately 25kB. On the C64 and Apple IIe, the TPA size is 46kB. Meanwhile, a BBC Tube system can provide just under 57kB, which is quite impressive.
Users can cross-assemble programs from a PC and also use a working C toolchain with llvm-mos. While there is a basic assembler for native development, there is currently no functioning editor.
Given has made it clear in his statement on Github that the port of CP/M does not allow users to run 8080 programs on the 6502. However, the relocation support in this port means that users can run unmodified binaries on any 6502-based system.
For more information about the 6502 port of Digital Research’s CP/M or for the current beta releases, check out the Github page at:
https://github.com/davidgiven/cpm65
