Also, for a little bit of misc fun: attached is Altirra's internal firmware, renamed to standard emulator names. I haven't tried the OS firmware on real hardware yet, but I did find the bug that was preventing the LLE OS from running on Atari800WinPLus 4.0: it wasn't handling COLDST properly and didn't force a cold start on a reset after a previous failed cold start. Apparently, the Atari800 1.x core doesn't clear memory on a cold start, so PUPBT* isn't reset, but COLDST is (!).

Regarding the drive emulation... that sounds like it may be a bit too esoteric for me to add, particularly if the drive emulation doesn't actually do anything with the flashed image. However, I have been thinking about ways to implement easily programmable test devices. For instance, it was pretty hard to test OS CIO device polling functionality, because no one seems to have actually ever created such a device that uses it.