I used to be really excited about getting into four cylinder OBDII stuff. I may have more information at home. I believe the pcm's are flash based.

There is some discussion on hptuners forum.

"01+ use basically the same hardware as ls1's whereas the pre 01 s-series use and older style computer from what I understand...thats why hptuners was able to easily get the 01+ stuff to the market...I dont think the market is there for pre 01 stuff if they would have to re crack code basically."
https://forum.hptuners.com/showthrea...8-S-10-Support


more bits and pieces here:
https://forum.hptuners.com/showthrea...e-votes-are-in!

I realize this is not highly technical. It does give some reading material and may help you find the information you're looking for.