SGI: Hardware

So, I picked up an MXI board for relatively cheap but I think one of the two TRAMs is bad on it. It fails IDE in "mg_tram_rev_nobuff", and any GL stuff using hardware textures shows up "interlaced" - see photos for examples.





I've tried reseating the TRAMs and swapping them between the two positions and I get the same failure mode. I ended up just taking them out and have it running in SSI mode, which passes IDE fine.

A couple questions: Is there any fix for this, or do I need to go hunting for a replacement TRAM? Any way to tell which TRAM is bad? I don't have an SI card to swap them into to test them individually.

You can try taking the heatsinks off and re-padding the chips, or check for corrosion.

Well that's just typical TRAM misbehavior. Like the wiki page says, they're "expensive and fragile."

It looks like one of your TRAMs is faulty, resulting in the interleaved pattern.

I would run the IDE diagnostics from the PROM menu, from a serial console if you can. See if it narrows down the problem to one of the two modules. Leave the other one alone, because whatever you do can only hurt it. I've never seen a faulty Octane TRAM (yet), but have 'fixed' MXE TRAMs by cleaning the contacts of the connector with a bit of pure alcohol and reseating the TRAM a couple of times while the connector was still wet.

I've seen similar problems with the Indigo2 IMPACT TRAMs and they were caused by mechanical and/or thermal stress on the TRAM modules. The TRAM chips are QFP chips, not BGAs (what you typically see these days). They are sensitive to PCB warping etc, causing solder joints to crack, pins to lift or make bad contact. I've reworked failed Indigo2 TRAMs before: viewtopic.php?f=3&t=16728901

The Octane TRAMs are a much better design than the Indigo2 TRAMs, the heat sink provides mechanical stability.

Raion-Fox wrote: You can try taking the heatsinks off and re-padding the chips, or check for corrosion.

Re-padding the chips is not going to fix a bad contact. But the mechanical stress of pulling the pad off a QFP chip after being stuck for 20 years might very well cause more bad soldering joints. So I would not do this, unless you have no other choice.

If you really have a faulty TRAM and you feel up to it, you could try what I did for the Indigo2 TRAMs. But even with a lab and knowledgeable people to guide me my success rate was only ~ 50%.

the IDE tests do not reveal which TRAM is bad, it simply says "tram test failed" and says the whole MXI assembly is bad:



030-0957-003 is the SSI/MXI mainboard, of course. When running IDE without the TRAMs it passes all tests.

I've done some swapping around of the modules to try and isolate the bad one, and I am starting to think that the problem lays with the mainboard itself and not the TRAM modules.

Obviously there are two positions for TRAMs, and the one in the position furthest away from the 13W3 connector always runs significantly hotter than the one closer to the 13W3. This makes me think that the TRAM modules themselves are fine but there is an issue with the other TRAM socket. Sound reasonable?

The board has been pretty significantly factory bodged, presumably to correct for design errors. The bodges don't look to have failed or anything, though. On this photo, it's the socket on the left that runs the TRAM hot, the one on the right does not get very hot.



The TRAMs themselves, both 034-0961-001 models:



I'll have to do a little more fiddling with it to see if there's connector issues and I'll have to take a closer look at the bodges to see if that may be contributing to the problem.

After doing some more experimentation I'm back to thinking one of the TRAMs is indeed bad. I haven't worked out a way to figure out which one is bad (aside from either buying a SI card to see which one doesn't work right in it, or buying another TRAM that is hopefully good).

I think it definitely is one of the two TRAMs though because if you swap the TRAMs to the opposite position, the "interlacing" pattern switches between odd/even lines on display. For instance in the Buttonfly demo it applies a texture to the buttons and the text itself is drawn from textures. I took screenshots between swapping the TRAMs into opposite positions and this is what I get:



zoomed in, split-screen:


I guess another question I have is... can I mix/match SI/SE trams on an MXI? Or do they both have to be the older SI trams to work?