ATtiny85 Boots CP/M by Emulating Intel 8080

For retro computing fans in England and beyond, this is a neat reminder that old hardware ideas still have plenty of life left in them. Ted Fried has built an Intel 8080 emulator that runs on an ATtiny85 microcontroller, and it is able to boot CP/M.

The ATtiny85 is a very small 8-bit chip, with 8 kilobytes of flash memory and 512 bytes of RAM. The Intel 8080, released in 1974, was one of the key processors of the early personal computer era, so getting it to run on such limited hardware is a serious technical feat.

To make the project work, Fried uses SPI for communication rather than direct parallel connections. Support tasks, including input and output, are handled by a Teensy development board, while the emulator itself is written in highly optimised C.

A 128-byte cache also plays an important part in the build. It helps speed up memory access, and the result is emulation that is only marginally slower than a physical 8080 when booting CP/M, also known as Control Programme for Microcomputers.

The project was reported by Hackaday, and the write-up includes fake 1975 electronics magazine covers for a bit of period charm. The code and hardware schematics are available on GitHub for anyone who wants to study the build further.

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