[jan-jaap]

I'm trying to restore this ancient machine (a 4D/70 GT) to working order. When I got it, it wasn't functional. It may even have been used as a parts donor.

But I got past the obvious, like the malfunctioning power supply and broken fans. The machine will power up and POST:



I can boot it in single user mode to a login prompt on the graphics console. But when I try to boot to the standard NeWS or X11 login, I get a bus error on an address related to the GM1 board and the machine panics.

I tried swapping the IP4 CPU board and the GM1 board. No result. I do not have any other spare parts for this machine.

I pulled the GT graphics boards, and installed them in a PowerSeries. That is, all of them except the GM1 board, because a PowerSeries has a different backplane and requires a GM2 board. The result is a PowerSeries GTX. It works and doesn't suffer from pixel errors. It passes the Field diagnostics. So the GE4, RM1 and RV boards of the GT graphics card set should be good.

The Professional IRIS itself passes the 'ide' diagnostics, but those do not exercise the graphics. But I think the IP4 CPU board(s) should be good too.

This only leaves the GM1 Geometry Manager board.

I have a hard time believing I somehow have two GM1 boards broken in exactly the same way. I suspect an incompatibility between the system firmware revision and the GT graphics board set. There are four EPROM chips on the IP4 board: 070-0093-010, 070-0094-010, 070-0095-010 and 070-0096-010. The PROM version is:

Code:

Version 4D1-3.1 PROM IP4 OPT Thu Dec 8 16:12:10 PST 1988 SGI

This predates the GT graphics. I do not have the older 'G' graphics to confirm, and parts for this machine are not easily found (to put it mildly).

So, how to proceed? I can see a few options:

• Someone has a Professional IRIS which works or used to work. We compare part numbers, and possibly eliminate my suspected incompatibility.
  
• Someone has an IP4 CPU board with later firmware than mine. We dump it and I try again.
  
• If someone knows someone who has one of these, please forward me their email address. There are very few people left who have one of these things.
  
• I'm open to suggestions.
  

Help!