Can a Mac Pro boot with a failed logic board?

Discussion in 'Mac Pro' started by iBug2, Oct 13, 2009.

  1. iBug2 macrumors 68040

    Jun 12, 2005
    My 8800GT went kaputt (screen jagged up and crashes during boot under OS X) so I replaced it with GTX285, which only worked for 2 hours and then machine shut down and didn't power up again with 285 in. But I could still power up AND boot Windows with 8800GT, even if the screen is all jagged up. (Mac OS X doesn't boot, it crashes during boot with 8800GT).

    I take it to the apple store in France/Lyon and they tell me they think it's the logic board which has failed. They'll order one, and try, and if it works, I pay, if it doesn't I don't pay.

    I told them that the logic board couldn't have failed since the machine boots into Windows without any issues, and I can use the machine on Windows. It recognizes both CPU's and all the RAM, I even did a Geekbench test in Windows.

    What I suspected was Power Supply but they said Power Supply is fine. But checking power supply is a long procedure, almost takes an entire day to watch and record all the voltage inputs/outputs. It's not a simple task, which I highly doubt they did or even aware of.

    Now, my question is, Can a Mac Pro boot into Windows and be usable with a failed logic board? Have you ever heard of such a thing? I could even use that machine in Target Mode from my MBP. 99% a working Target Mode means all the I/O on the machine is working perfectly fine.
  2. Cindori macrumors 68040


    Jan 17, 2008
  3. iBug2 thread starter macrumors 68040

    Jun 12, 2005
  4. Cindori macrumors 68040


    Jan 17, 2008
    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:

    only keeping url open for a few mins, so download it while you can.
  5. Dr.Pants macrumors 65816


    Jan 8, 2009
    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.
  6. iBug2 thread starter macrumors 68040

    Jun 12, 2005
    No I mean by irrelevant I meant I obviously tried that. I have 4 OS X installs + Apple boot DVD. All behave the same way, as expected. And the reason OS X crashes on boot and Windows boots with failed 8800gt is because Windows doesn't require the video card functioning 100% but OS X checks on that and doesn't boot with it. (I assume).

    And no. Obviously there is something wrong with hardware, since the machine doesn't even power up when GTX285 is installed. Either 285 is dead with 2 hours of use (very very unlikely) or PowerSupply/Logiboard has failed. Apple service like I said suspected logic board, but I don't think windows can boot if logic board has failed and target mode is working.
  7. gugucom macrumors 68020


    May 21, 2009
    Munich, Germany
    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.
  8. nanofrog macrumors G4

    May 6, 2008
    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. :eek: They still work sometimes though (they only do a basic power up test).
  9. iBug2 thread starter macrumors 68040

    Jun 12, 2005
    No no, I never said 285 is working under windows. With 285 connected to power feeds, the Mac Pro doesn't power up at all I said. And the OS isn't the issue. The Mac Pro does not boot with 8800 from any of the OS X disks, including Apple Installer DVD.

    So if anyone has heard something like "half failed logic board" before say please. Because I really don't think there can be anything wrong with the board if windows boots and works with the failed 8800.

    About PSU, that's the only thing that's left. CPU's must be intact, again Windows boots and runs Geekbench and Geekbench recognizes both CPU's, and the performance is as expected. RAM is working, again Geekbench. The video cards are dying one by one, and I bet if I install another new card in it'll die too.

    So what's left? I've only heard half broken PSU's killing system components one by one. I never heard a broken logicboard booting OS's but killing video cards.
  10. nanofrog macrumors G4

    May 6, 2008
    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.
  11. iBug2 thread starter macrumors 68040

    Jun 12, 2005

    8800GT is half functional under Windows. The screen is jagged, it seems like it's displaying only 256 colors, and windows does not recognize the cards hardware. It only sees it as generic video card. No acceleration.

    If I try to boot OS X with 8800GT I get the jagged screen for 1 minute, I see the grey Apple logo, shifted to left of the screen, and then the kernel panic window (Please reboot your system using power button etc etc).

    That's 8800GT.

    You say the board is most probably fine. But if it's the PSU how to make sure? I might as well order a new PSU (it's the cheapest component anyway) and keep using the system with a new video card, and hope that the new card doesn't fail. If the system works with a new card long enough under heavy load (gaming etc) I'd say it's ok.

    And do you think the GTX285 will be covered under warranty? After all, it's my failed PSU or logic board which 99% killed the card.

    Oh and one more thing. The diagnostic LED's on the logic board. When GTX285 is connected, when I hit the power button, nothing happens but I hear a clicking noise, and a red LED lights up right beside the power feeds on the board which go to the card. I know that all those LED's on the board mean something when they light up but I couldn't find which LED is for what. But still, that's another clue.
  12. nanofrog macrumors G4

    May 6, 2008
    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. :eek:

    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). :rolleyes:
  13. iBug2 thread starter macrumors 68040

    Jun 12, 2005

    Now, first of all, no more Apple Care. I didn't purchase Apple Care and the computer is more than 1 year old.

    Second, I won't replace 8800GT, I purchased GTX285 last week after 8800 died, I purchased it from OWC Macsales and I emailed them and they already issued an RMA, so I'll return the card and they'll ship a new one. But I'll of course pay for the shipping and possible customs. (I live in France, purchased the card from USA)

    About another working card, I already ordered a 4870 from Apple Store France, just to be on the safe side (have another working GPU at home when I need it). So I'll use 4870 until the replacement GTX285 arrives. And that 4870 should arrive today.

    So you think the most reasonable course of action would be to go to the stupid Apple repair service here, and explain to them that the logicboard is not dead so they don't need to order another one to replace it. Instead they should order a new PSU, replace it, give the machine to me and let me test it further with the 4870.

    Am I right so far?

    About a secondary PSU, the store does not keep one in handy, but they told me they checked the PSU and it's fine. But I really really really really doubt they ran any actual diagnostics on the PSU other than powering up and saying hey it works. Considering they "tested" my logic board with a Radeon X1900XT (Which if not firmware upgraded won't run on early 2008 Mac Pro's) and said "hey your mac doesn't boot with a X1900XT so logic board must be gone", they have pretty much no clue about computers nor macs.
  14. nanofrog macrumors G4

    May 6, 2008
    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. :D

    :cool: 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. :p

    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.
  15. iBug2 thread starter macrumors 68040

    Jun 12, 2005
    I'll go to them and say order a PSU and don't install the logic board yet. Just hold on to it. When the new PSU arrives I'll take the Mac Pro at home and use with the new PSU. If the 4870 boots both OS X and Windows and works under heavy load, can I then make sure the logic board is ok?

    And one more thing. When I replace the PSU, if the Mac Pro boots OS X with 4870, can a damaged logic board fry that 4870 as well? Or if the logic board is also failed, it won't just boot at all?

    Edit: Went to the store and told them to order a PSU, put it in, and call me. I'll bring 4870, test if the system boots OS X, if it does, take the Mac Pro home, use it couple days, and if all is fine that's it. Otherwise I'll take it back and install new logicboard as well.
  16. nanofrog macrumors G4

    May 6, 2008
    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).

    :cool: Good luck with this.

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

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