Comment by Gibbon1
14 hours ago
I used san RTOS written in assembly for the Atmel AVR. AvrX (by John Barello)
You can look at the code here.
https://github.com/kororos/AvrX
Compiles down under 2k.
The thing is while actually doing that isn't crazy hard, they did that with hardly any existing examples to go by. And without modern tools.
And with a ROM that had to be hand sewn. No flash updates, just "little old ladies" working in a former bra factory for a defense contractor (and huge tax payer expense if any mistakes needed to be debugged).