Modern microcontrollers are becoming quite beefy. The Microchip PIC32 line is actually an implementation of the MIPS32 4K architecture - and with 512K of flash and 128K of RAM you can even run Unix! RetroBSD is a port of BSD 2.11 for the PIC32. You might not be able to run X11, but it is still very useful and a great reminder of how small Unix used to be - and how far it has come.
posted by jockm on Tue 19th Aug 2014 21:31 UTC