HP 9836 & 9836U

AFAIK the only difference is the CPU board, which is a plug-in PCB , not the motherboard. There are several differences betwee teh 9836 and 9836U CPU boards : The CPU : 68000 .vs. 68010 THe clock rate. I forget the 9836 clock rate, the 9836U clocks at 12.5MHz RAM on the CPU board. A plain 9836 may have RAM on the CPU board (64K, 128K), a 9836U does not (there wasn't space!) MMU. The 9836U has a MMU circuit o nthe CPU board (this is not a standard IC, it's a lot or small RAMs, TTL and a few PALs Cache RAM. The 9836U has a (small) cache on the CPU board Both machines came in A (monochrome) and C (colour) video versiobs. The difference here is the monitor and the 2 video PCBs (text and graphics) uder the left hand floppy drive. Note that you van't use the 'wrong' monitor with a particualr machine The other parts (motherboard (which includes HPIB and keyboard interfaces), PSU, floppy controller, drives, I/O cards, etc) are the same AFAIK. -tony