I followed up the TI thing with Bell in Edinburgh and he replied as follows:
"Hmm, i've thought about it, but i can't say i've tried. I've got an 89, so i'll have a look into it.
One problem is that the memory you're restricted to is 188k. Maybe this could be gotten round if you paged data in and out of the flash memory, which is 2.7 megs. However, this would probably be difficult. You'd probably be able to get away with running OS's up to System 3.3, as this is what the Mac 128K supported.
Another (and probably much bigger problem) is getting it to use the video hardware of the calculator. I have no idea how you'd get it to do this, especially as it isn't open source like Linux. Btw, that reminds me: if you were thinking maybe Linux might work on a TI calc, think again. There's almost certainly no way to do this. That said, I'm thinking of implementing a TCP/IP stack on my 89 so I can use it as a web server. Might even work
Also, you'd have to mess around with the kernel to tell it where load main storage from. This isn't as tricky as it sounds though. Maybe the best thing to do would be to find a copy of System 3.3 and try to disassemble it."
"Hmm, i've thought about it, but i can't say i've tried. I've got an 89, so i'll have a look into it.
One problem is that the memory you're restricted to is 188k. Maybe this could be gotten round if you paged data in and out of the flash memory, which is 2.7 megs. However, this would probably be difficult. You'd probably be able to get away with running OS's up to System 3.3, as this is what the Mac 128K supported.
Another (and probably much bigger problem) is getting it to use the video hardware of the calculator. I have no idea how you'd get it to do this, especially as it isn't open source like Linux. Btw, that reminds me: if you were thinking maybe Linux might work on a TI calc, think again. There's almost certainly no way to do this. That said, I'm thinking of implementing a TCP/IP stack on my 89 so I can use it as a web server. Might even work
Also, you'd have to mess around with the kernel to tell it where load main storage from. This isn't as tricky as it sounds though. Maybe the best thing to do would be to find a copy of System 3.3 and try to disassemble it."