[jan-jaap]

On second thought I changed my mind. It is not an IP9 board. This is an IP9:



Obviously the layout is very different.

Now, back to your board. A few things stand out:

• Memory is 9 chip, 30 pins. SGI only used that in the Professional IRIS and the early Personal IRIS (4D/2x). PowerSeries used proprietary RAM.
  
• There's an integrated SCSI controller. PowerSeries always used an IO2 or IO3.
  
• It's not an IP4 board (Professiona IRIS) though. Those ran at 8 or 12MHz, this runs at 25MHz. This is an IP4 board:
  

It's similar, though. I don't think is an IP4.5 (4D/80 "OmniIRIS") board either, those ran at 16MHz.

Finally, it could be a variant on the Personal IRIS. The HPC1 chip hints at that. However, no Personal IRIS ever ran at 25MHz either, and the VME versions of the Personal IRIS (V20 ... V35) were all 6U VME boards.

Intriguing. Want to sell it? I'll put it in a 9U VME enclosure, see what happens. If it is a Personal IRIS variant this could be tricky: those map the GIO32 bus to the VME P2 connector, so whatever else is in the chassis better not cause any shorts with that ...