[CB_HK]

There are also a lot of jumpers on these boards. My 4D/50 board seems to match the board on Gerhard Lenerz site.

I didn't connect to the GM1 diagnostics port yet. Tried that once with a VGX and I didn't get very far.

While I have absolutely no expertise in this area (and its debatable what I do have when it comes to SGI) I would say that hooking up to the diagnostics port should at the very least let you know if the board itself is alive and if it's having any particular issues. When I hook up to my VGXT setup I can see all the boards going through their boot phase and I get a pass indication. Not sure if that's completely applicable to your case but it could at least help narrow things down a tiny bit more. Not sure if you had any trouble when you tried it yourself--I used the standard SGI terminal settings.

I hope someone here is able to get you the info you need. That's a really cool machine and I'd love to see it up and running.