Can a Mac Pro boot with a failed logic board?

I'd try installing OSX on another drive..

 

how come? you only get problems when booting osx and obviously nothing wrong with hardware (no, you can't boot windows or any other os without a logic board).

but I guess it doesnt cover the 285GTX problem.

here take this, this is what apple ppl themselves use to diagnose your mac:

http://groths.se/macpro.pdf

only keeping url open for a few mins, so download it while you can.

 

I would try OSX on another drive as a good starting point. Or do an Archive and Install if you have your files backed up. I would think that the OS somehow got corrupted if Windows works fine with all the hardware, like Cindori said.

 

I had a similar thing. Windows did boot and OS X went boom all the time. I knew it had something to do with a program that i downloaded because it told me it needed rosetta befor all the agro started. It turned out that the vendor had a Mac Pro and PPC version and had installed the wrong versions behind the download link.

My OS X 10.6.1 was running on an SSD RAID0 array on a ARC1210 card and when I checked it it said it was ok. I had a backup hard drive which I had used to install the RAID0 array. I installed the HDD and cloned it again on the array and all was fine again. Obviously I made sure next time I got the right program.

 

Very good point.

It would be worth trying, especially as the hardware appears to be working under Windows.

It certainly wouldn't be the logic board. From a previous thread, I had the impression that the PSU may have been damaged, but the way the OP has posted here, if the GTX285 is working under Windows, it's not dead either (neither the PSU or GTX285). Not so sure on the 8800 though (previous thread).

I'd be amazed if Apple does a proper load test on the PSU. It takes quite a bit of time, and you don't have any original test data to compare it to. It still helps to determine if it's within specs (and more obvious issues, but these can be tested without a proper load test), but surprisingly, many new ones aren't in spec from day one. They still work sometimes though (they only do a basic power up test).

 

For some reason, I was thinking the 8800 worked, but had issues (wonky output). So I figured it was bad. Could you elaborate here?

I was also under the impression the 285 was functional under Windows. Sorry about that, I hadn't gone back and checked the previous thread. Since it's not working at all, I'd think it's definitely DOA.

With the logic board: It's possible the PCB traces are shorted. They're finished in HAL (Hot Air Leveling, which is a layer of solder applied to the board prior to the stuffing and soldering down of a single component). If they overheat, they can melt this solder layer, and it bridges from one trace to another. This will happen if the current draw is too high for the size of the trace. I'd need detailed pics to even attempt to determine if that happened. So there's no way to really tell at this point. So technically, it's possible, though less rare than other issues.

BTW, if this did happen, it will kill the PSU. At least any rail that's connected to the shorted traces for certain, so it could be partially functional. But the way most are made, they're interconnected to some extent, and tend to cascade (all the rails go, and the whole thing is DOA).

The CPU's are good, as are the Voltage regs, etc... from what I understand.

You've a mess on your hands, and the only way to really find out, is by having some good working parts to test it with. Another 285 would suffice. I am getting the impression the PSU is going though (PCB traces on the logic board are good, so you don't need a new board). Failing rails (overvolt or under current on say the +12V rails attached via the logic board traces) can take out a graphics card/s.

 

It sounds like the 8800 is essentially dead, and needs to be replaced. But before you go buying parts, you need to properly diagnose it, and I need to know a few things.

1. Do you have any Apple Care left?
2. Was all of the parts in the system from day 1 (BTO system with both graphics cards), or was the GTX285 a later addition?
3. Can you obtain the use of another graphics card (ideally another 285 or similar that would use the logic board's PCIe power to run it)?

The reason is, if you're paying for all of the parts (no more Apple Care), you could end up buying what you don't need. For example, you may not really even have to use the 8800 any longer, and eliminating it would save you money. The PSU seems extremely likely (fails under load), but it's possible just both of the graphics cards are dead.

But the logic board seems fine. Unless you're diagnosing it with working parts though, do NOT run it. A bad PSU can take the logic board, and other items such as the CPU/s and memory with it as well.

The GTX285 is likely dead, but I can't be sure. That's why you need a working card to test with. The PSU seems dead, and the primary reasons for the issues of late (at least a bad pair of rails).

Now how it happend (what took out what, is debatable). But you don't know if the current GTX285 is actually good or not. I'm presuming you may be/are willing to live without the 8800.

If everything is covered by AppleCare, then they should be doing all the diagnostics, and pay for any needed parts they installed at the time you ordered the system (what Apple Care would cover). If the GTX285 was an add-in, even if it was purchased from Apple, would almost certainly be bounced back to EVGA, as they actually made the card, unless you just recently got it (within Apple's return/RMA policy).

Details are needed, as is at least another graphics card. A PSU would help too, but I presume you can't get one. Apple would have to do this, and i've no idea if the store keeps one around for diagnostic purposes (I'd have thought so, but not so sure, given some of the posts I've seen in other threads).

 

I just wanted to make sure, to avoid any issues. Sorry you're stuck with the bill on the original system parts that are dead.

Cheaper than having to buy another one though.

This is your "guinea pig". Install it in the system, and see if you can get it to boot for both OS X and Windows. My guess, it's going to fail due to the PSU.

On the odd note it works for both OS's, retest the daylights out of it to be sure. Load the card with anything you can throw at it, to see if the rail/s are partially functional, but crap out before they reach their full load (or whatever the card can "suck" from them).

Test the HD4870 first, and see what happens. If it does what I think (fail to boot, no matter what you do), then explain this to them. Remind them that the logic board will still boot under certain conditions, and it's all graphics card related. If they still don't get the hint, then spell it out in simple terms it's the PSU, and to order it. They can hold onto the logic board, just in case it's a shorted trace.

To properly diagnose it on their end, they need a PSU, logic board,... (all known to be good), and go from there, as they don't put it on an electronics bench, and bring out the heavy artillery (Digital Multimeters, Bench PSU/s, Oscilloscope, Load Meter,...). I've never seen such tools there. Maybe they're hidden in a closet gathering dust. I don't know, but I've not had the impression that the Genius's would even know what they were, let alone how to use them.

They can't do this, so you'll have to wait for the PSU. Once it shows up, get it installed, and re-test the graphics card/s and see what happens. I'm pretty sure that will solve your problem, from what you've described (and unable to look at it myself).

If not, then install the logic board, and go again. If it works, then place the old PSU in and re-test yet again. This would determine if it was the pair (logic board + PSU), not just one or the other. I seriously doubt this, but it can happen. There's usually a clue or two, such as melted wire insulation, a PSU that glows red followed by bursting into flames,.... No joke. There's smells as well if it didn't get that far, as well as the behavior (or lack of).

Somehow, I doubt their diagnostic skills at this point. That simple a power test isn't adequate, as they're under the impression it either powers up or not. That's not always the case. There's no way they actually had a 980W load and then measured the outputs (you also run the load long enough to heat up the sinks to Tload).

And any testing in your case needs to be with a graphics card that requires both of the PCIe power connectors, and load the card as hard as you can. Anything that just uses the PCIe slot (no power cables) is a joke, as those are the rails in question, given the system's behavior. Hence why I don't think those you've been dealing with really understand what they're doing.

Just make them hold onto the logic board while they wait for a PSU. They should have had enough sense to get both in the first place, as either is a possibility. No matter if it's warranty work or paid service. Whatever they don't use, they can send back to the parts warehouse.

If they want you to pay for the shipping on a part that isn't used, I don't agree with it, but if it gets you your system back in working condition, it would be worth it IMO.

 

Re-test it when you get the replacement GTX285 to be sure it will work with that particular card, but if it boots and remains functional with the HD4870, then I'd think you'll be fine.

It's technically possible, but that would be rare I would think, given it's at least trying to function with the 8800 in Windows. Boots OS X, but no display at all.

BTW, any other PCIe cards in the system? If the board were to be the problem, these should fail out as well (damage occurs off the PCIe slot itself; i.e overvolt on the PCIe bus).

Good luck with this.

Did they give you any idea as to how long it will take to get the PSU in and installed?