It appears a very important anniversary passed by recently without anyone realizing. The January 1975 issue of Popular Electronics featured the Altair 8800 on the cover, otherwise known as the blinky box that launched a revolution, the machine that made Microsoft a software powerhouse, and the progenitor of the S-100 bus. The 40-year anniversary of the Altair wasn’t forgotten by [dankar], who built a front panel emulator with the help of some much more modern components.

The build unofficially began with an Intel 8080 emulator written for an Arduino. The 8080 is the brains of the Altair, and while emulators are cool, they don’t have the nerd cred of a panel of switches and LEDs. The hardware began as a bunch of perfboard, but [dankar] wired himself into a corner and decided to make a real schematic and PCB in KiCAD.

Despite the banks of LEDs and switches, there really isn’t much to this front panel. Everything is controlled by shift registers, but there is a small amount of SRAM in the form of an SPI-capable 23LC1024. This comes in handy, because [dankar] is running CP/M 2.2 on this front panel emulator from disk images saved on an SD card. Everything you would want from a computer from 1975 is there; an OS, BASIC, and enough I/O to attach some peripherals.

[Gary Kildall] and CP/M are the great ‘also ran’ of the computing world; CP/M could run on thousands of different 1980s computers, and [Gary] saw a few million in revenue each year thanks to CP/M’s popularity. Microsoft, DOS, and circumstances have relegated [Kildall] and CP/M to a rather long footnote in the history of microcomputers, but that doesn’t mean CP/M is completely dead yet. [Marcelo] wrote a Z80 emulator running CP/M inside an Arduino Due, and he did it in such a way that it’s actually convenient and useful to use.

Instead of using CP/M disk images, [Marcelo]’s emulator emulates CP/M disk drives on top of a regular FAT file system. Drives are mapped to folders in the FAT file system, so a folder named ‘A’ will show up as the A: disk in CP/M. Drives up to P: are supported, the maximum number of drives available under CP/M. The BIOS resides in the root directory of the SD card, and so far Microsoft Basic, Turbo Pascal, UCD Micromumps, and Wordstar work just fine.

The Arduino project was built upon one of [Marcelo]’s earlier projects that put the CP/M emulator on Windows. The version for the Due works exactly how you think it would, with a serial connection and terminal emulator providing the IO, and the huge amount of processing power and RAM available on the Due doing all the heavy lifting.