http://retrobsd.org/wiki/doku.php
requires 512KB of flash and 128KB of ram
Wow. But let me ask a noob question:
While it is highly impressive to see a UNIX implementation running in 128 K RAM - what would be the benefit of it putting in as the underlying layer into an EC? 512 / 128 K is still probably a bit more than average in a µC (well, at least for the relatively small things that I know) and you'll have then used all the memory already for RetroBSD. Now what would be the benefit? Will this facilitate programming for the fan control, charging, Super-I/O and so on? I guess the programming work would be quite similar, because e.g. the logic to charge a battery will still stay the same. But then, why add another layer?
But it is impressive either way. Looks like there was some efficient programming going on.