[weblacky]

That being said it should be noted that most of the time SGI mainboards are powered by the 3.3 V and 5 V power lines of the power supply. They don't usually care about the 12 V line. The 12 V line is normally what powers your fans, the hard drives (along with 5V), and a lot of big ticket peripherals via VRMs. Now it's possible the graphics don't use the 12 V line, this has not been investigated on Octane and of course on other machines such as indigo2 IMPACT, it has special graphics connectors to get 3.3 V power at high amperage and doesn't use a VRM to step down a 12V source.  The Octane peripheral connectors have similar special connectors on the back point just for high amperage power. So I assume that they have their own mechanism for delivering low-voltage, high amperage, power from the power supply to the peripheral connections.

However as a later design, in the octane it would make sense if the power hungry graphics card we're stepping down the 12 V source as you would see in today's peripherals.

Octane power supplies are the latest current trend in failing, and requested, parts. Though I do agree with Raion in that we normally don't see octane power supplies degrade slowly. They normally just stop one day usually their protection circuitry kicks in. But that doesn't totally rule out that one of the power rails in the octane power supply is not performing correctly.

The IBM hard drive you specified has detailed requirements in its manual that actually says "12V + / - 7% is acceptable during spin up". And the drive itself is supposed to only allow a 5% variation on its DC power input.  It also claims that it will not accept more than 150 mV pp on the 12V line.

If you don't have another system that supports SCA 80, and you don't have an adapter card that at least lets you plug in a normal PC Molex connector to test the drive spin up then it is hard to know whether the drive itself has gone or whether it's a power issue.

The octane also has one of the largest number of electrolytic capacitors on its mainboard compared to nearly every other SGI I've seen. Now they use a solid aluminum electrolytic that doesn't leak out, but they're not polycaps.  I had assumed in the next few years that octane motherboard recapping would probably be required given the enormous amount of capacitors all over the thing.

I would say though without further information, and certainly I have had ram go bad in an SGI and an old PC that old, previously working, memory failure is super rare but it happens. Outside the RAM what it sounds like is bad power. If you can keep rebooting it and things start working that's normally a sign that the power supply or system VRMs are trying their best but not keeping up at their end of the bargain. And the fact you were running fine for a month until the errors started to happen would also lead me to believe that it's power related. That being said those graphics cards run hot and it could just as well be cracking solder joints. But I feel like the proliferation of problems all around the system points more to power than it points to the graphics because you're having more problems than just the graphics card. Granted I'm putting the hard drive aside on this one because you should try to test the hard drive spin up using a SCA 80 SCSI adapter.  If you can spin up just fine on an adapter with a normal PC power supply then I would definitely start blaming the power system in the octane.

Unlike my adventures in Indy, I've not gotten to the octane power supplies yet as there's other things to do and I'm still setting up equipment and setting up workflows for repairs in general. Octane is probably the hottest topic here on the forums in regards to people wanting power supplies and people needing troubleshooting help. Because right now they are the sweet spot in the economy of SGI collecting.

Right now what I would suggest is perhaps to put it aside until you're able to secure a known good power supply. Unfortunately every power supply you come across is going to be nearly 30 years old. So a working one would still only get you by for maybe a few weeks or months before this would may happen again.

I recommend that you maybe put it to bed and keep watching the forums when one of us starts offering a rebuilt octane power supply, which unfortunately is going to be a little while. I also don't think they'll be cheap. The octane power supply is heavy, dense, has quite a number of PCBs in it, and likely will be that much more difficult to fully rebuild and reconstruct correctly along with the proper adhesive and testing.  Octane is also one of the few power supplies that is oversized in shipping, in its length dimension.

Octane power supplies are on the verge of what we would call smart, they do have some overcurrent and overvoltage protection in them but they're not as smart as a modern power supply today. We've definitely seen where they will cause charred damage to the connectors on an octane during a surge or malfunction. It's rare but we have seen it, so that means that the octane protection mechanisms do not generally encompass all the scenarios you might encounter related to a malfunction.

I would say it's worth keeping an octane but similar to your Indy I think you'll need to wait for refurbish power supplies to come online unless you want to try to hunt down another used octane power supply you think you can trust just for testing purposes. Either way any power supply you get will be so old that if you wish to use it very frequently in the foreseeable future the power supply could not be trusted, without some level of refurbishment at at least the filters/capacitors level.