[jan-jaap]

This 4D/50 'G' keeps fighting me every step of the way. By now the entire system is more or less back together. The PSU is stable, I replaced the dead system disk with a more or less period correct 300MB full height brick that tested good. The tape drive is unusable (capstan turned liquid). The graphics have left the chat it seems and there's no ethernet. I thought I'd cheat it by installing a known good IP4 and booting it off a harddisk with an IRIX 4.01 image dd-ed to it, but it refuses to acknowledge the disk is even there. Of course the 4D1-2.1 PROM doesn't even know the hinv command but while the 4D1-3.1 PROM does, it doesn't show any SCSI devices.

Basically the IP4 I borrowed from my other Professional IRIS takes power from the backplane and talks on serial and nothing else shows any signs of life. I'm starting to suspect the backplane. And about that backplane: these things are very sensitive to correct jumpering of the IACK/BG jumpers. Without it you get interrupt problems which means system crashes. I had a similar problem when I got my first Professional IRIS (See here and down), but that one had clearly been tampered with and then discarded to rot in a warehouse. This one looked pristine and untouched. Still, the IACK and BG jumpers of slot #9 are missing which means a card must be installed there. But there wasn't one, the graphics were in 10, 11 and 12. This can't work...

   

It should have detected the graphics with or without IACK/BG jumpers though. It probes graphics by looking for a magic value at a certain address in memory.

I think I may need to tackle this the other way around: start moving bits of the 'new' Professional IRIS 4D/50 into my existing 4D/70 to test them individually. Who knows, maybe the 'G' graphics work after all