March 11, 2022

Silicon Graphics Multibus "IP2" board -- PAL devices

The IP2 board contains quite a number of PAL devices. It count 27, but I may have missed some. Usually this is a nightmare for someone trying to reverse engineer a board like this, and it is certainly more work.

So far I have checked 3 and the security fuses were not blown! This is great news, because I can read them out and then use PALASM (once I get it running again) to decompile the JED files.

Here is a list based on the schematic 

U8  page 4, 16L8A-2 interrupt
u72 page 5, 16L8-15 segment0 decode  4a36
U71 page 5, 16L8-15 segment1 decode  59fb
U92 page 5, 16L8-15 system decode  6d0f
U76 page 8, 16R4    mouse
U84 page 8, 16C1    parity
U117 page 11, 16L8a-2 prom ctrl
U37 page 13, 16L8-15  mapa1
U38 page 13, 16L8-15  mapa1
U39 page 13, 16L8-15  mapa1
U40 page 13, 16L8-15  mapa1
U41 page 13, 16L8-15  mapa1  for 256M virtual space
U34 page 13, 16L8-15  mapa1
U89 page 16, 16L8A-2  limit0
U90 page 16, 16L8A-2  limit0
U85 page 16, 16L8A-2  limit1
U86 page 16, 16L8A-2  limit0
U83 page 16, 16L8-15  berr
U82 page 17, 16R8-15  memctrl
U174 page 17, 16L8-15  write
U4 page 18, 16L8A  slave
U27 page 18, AMPAL16L8A  master
U32 page 18, 16C1  mbprot
U26 page 18, TIBPAL16R6-15  busarb
U136 page 20, 16L8-15  swap
U137 page 20, 16L8-15  md
Feedback? Questions? Drop me a line!

Tom's Computer Info / tom@mmto.org