Make PowerMac G5 slave cpu the master?

Discussion in 'PowerPC Macs' started by StUPoT, Jan 1, 2013.

  1. StUPoT macrumors member

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    May 23, 2011
    #1
    Hi I have a Dual 1.8ghz powermac g5 and have been having trouble getting it to work. Through research and tinkering and am starting to think it's the CPU's causing the issue.

    My system seems to freeze around 20mins after boot up. I have tried running the computer on one CPU but it still happens.

    Now I have tried putting the slave CPU in the master slot but upon boot the fans kick in wildly. Is there anyway to make the slave CPU the master as I would like to see if it still freezes whilst running that CPU
     
  2. Zotaccian macrumors 6502a

    Zotaccian

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    Apr 25, 2012
    #2
    Sounds more like motherboard issue and G5's are known for those. Power supplies also go bad sometimes, but usually the machine will not start at all in that case, it varies though. There is one Apple designed chip (U3) on the backside of the motherboard which runs at insane temperatures, its solder connections are usually the reason why G5 PowerMacs start to behave like that, those connections crack causing the chip to be partially detached. Sometimes there is proper connection, sometimes not, temperature affects it greatly as metal expands it heat.

    Have you monitored temperatures or ran Apple Hardware Test or something else to reach the conclusion that it is a CPU fault? Does the machine crash faster if you run something CPU intensive?
     
  3. StUPoT thread starter macrumors member

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    May 23, 2011
    #3
    I recently put in a logicboard that was known to work fine but it's just doing the same as the one I took out now. So this led me to believe that the CPU's were causing the problem.
    I have however not put a huge load on it just mainly trying to put an OS on the thing which wouldn't cause the CPU's stress would it?
     
  4. MisterKeeks macrumors 68000

    MisterKeeks

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    #4
    It'll stress them a little, but it shouldn't freeze the computer.
     
  5. StUPoT thread starter macrumors member

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    #5
    Even so wouldn't this cause a crash if they are faulty?
     
  6. 666sheep macrumors 68040

    666sheep

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    #6
    Temperatures weren't an issue here. Source of this problem was crappy ROHS soldering. In fact, ROHS solder needs higher temperature to melt than regular lead one. FYI, northbridge in MP 1,1 and 2,1 runs all the time ~70C without issues, and it's rated by Intel to 80C max.

    But this isn't OP's case because of different symptoms.

    OP, get ASD 2.5.8. and run ll tests (it might take a while) and see what it will tell. To bring fans to normal speeds after CPU swap, run thermal calibration from ASD disc.
     
  7. Zotaccian macrumors 6502a

    Zotaccian

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    #7
    Higher temperatures cause greater expansion and if the chip would run cool even the crappy soldering would last longer. I'm well aware that the RoHS soldering (and cracking solder connection) is the issue on many motherboard failures as I'm currently using MBP with Nvidia 8600M which I fixed by reflowing it, if I had equipment and of course more skill, I would reball it with leaded solder. When I first experimented the reflow, the reflow worked flawlessly for approx. 7 months and it failed only after I played some online gaming (which I very very rarely do) which taxed the GPU to max and naturally made it run very hot. Greater the temperature, greater the expansion.

    When the solder is cracked, some people have had "success" with heating the chip location (backside) with hairdryer first and then they have been able to boot the machine or if it is a laptop, they have powered it on for while and put clothes etc. to intentionally overheating it, after that it has booted sometimes.
     
  8. 666sheep, Jan 4, 2013
    Last edited: Jan 4, 2013

    666sheep macrumors 68040

    666sheep

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    #8
    My point is, that temperature may be a factor, not the reason. G5 memory controller may run hot, but it does not exceed its thermal design. Otherwise none of PM G5 would even leave Apple factory.
     
  9. Zotaccian macrumors 6502a

    Zotaccian

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    #9
    Well yes that's what I pointed out in my earlier post:

     
  10. 666sheep macrumors 68040

    666sheep

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    #10
    Actually, you've put pressure on temperatures by your wording – "Insane". ;)

    ...and in fact they do run within specs (up to 90-105C maximum - see datasheet).
     
  11. Zotaccian macrumors 6502a

    Zotaccian

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    #11
    Well to me they are insane because all the PC's I've owned have chipset temps running less than half the temps than the chipset in PM G5. Also I've heard people saying that G5 runs pretty hot or insanely on iMac G5's even though it is still within thermal specs and the machine has not caught on fire :)

    When I watch Netflix or similar on my MBP the CPU temps rise fairly quickly near the 95C-100C and to me that's again, insanely high temperature even though the machine still runs while sounding like a jet engine.
     
  12. 666sheep macrumors 68040

    666sheep

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    #12
    iMac G5 had worst cooling desing I've ever seen TBH. However mine didn't burn when running 12 hour non-stop-Handbrake-encoding-torture test :) But I wouldn't call it quiet while running it. Anyways, solder shouldn't crack even @100C, especially lead-free one.
     
  13. Zotaccian macrumors 6502a

    Zotaccian

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    #13
    Well not at 100C, the problem is with the repeated heating and cooling cycles and the bigger the temperature is the more it has to cool down.

    When I played that game on my MBP, it worked fine many hours even though the temps were high pretty all the time. I had Skype conversation going on at the same time and my friend asked if someone is vacuuming nearby, had to reply that nope, it's just my Mac :rolleyes:

    And after I shut down and tried to boot again after couple hours, black screen. Very common way it happens.
     
  14. StUPoT thread starter macrumors member

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    May 23, 2011
    #14
    I've managed to get Tiger on the thing and had it running for about 30mins but then it froze again. So it is obviously getting to a certain temp that causes a connection to expand and disconnect. I guess I could take the board out and try heating the solder... Would this be better with a hair dryer or the oven method? I have had success with the oven method in the past with Mbp but I don't know how this g5 board would react?
     
  15. Zotaccian macrumors 6502a

    Zotaccian

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    #15
    Well with hairdryer you cannot melt the solder, the hairdryer worked sometimes in situations when there was no picture at all, sometimes heating it beforce attempting to boot expanded the solder just enough to create connection and the machine booted.

    I have never tried the owen method, only heat gun and with that the best "fix" has lasted 7 months. The best actual fix would be to reball, replace the solder material with better but to do that you need special equipment and skills.

    When I had my faulty G5, it would sometimes hang on boot and display DART Enabled as last message in verbose mode. When it booted it worked random times, sometimes couple minutes sometimes even hours. I noticed that Tiger worked better. Apple Hardware Test claimed that everything's fine no matter how many times you ran it so perhaps it did not truly tax the system.
     
  16. 666sheep macrumors 68040

    666sheep

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    #16
    Try ASD first, because:

    Baking/reflowing the board is against logic IMO at this stage of troubleshooting. Especially when symptoms are not clearly pointing on Northbridge being the culprit. No boot problems, no disappearing RAM. Did you check temperatures right before freezes? G5's do have a bunch of temperature sensors which can be monitored using Temperature Monitor for instance. Personally I think that it's one of CPUs. Been there, done that, symptoms were exactly that same as yours.
     
  17. StUPoT thread starter macrumors member

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    May 23, 2011
    #17
    I'll have a look at the ASD again and go through all the temperatures.
    I have only used the ASD before to try and calibrate the CPU's but it calibrated one and half way through calibrating the 2nd it froze again.
     
  18. StUPoT thread starter macrumors member

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    May 23, 2011
    #18
    It's now working fine...
    I replaced the CPU that was in there with the 2nd one and thermally calibrated it to the top slot. After that everything works perfectly apart from it only having 1 CPU.
    So it was CPU failure
     
  19. 666sheep, Jan 8, 2013
    Last edited: Jan 8, 2013

    666sheep macrumors 68040

    666sheep

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    #19
    Great. If you want to buy replacement CPU, check which revision of CPU you have. Basically 1.8DP were: 8 RAM slots (2003) = PowerPC 970, 4 RAM slots (2004) = PowerPC 970FX.
     
  20. StUPoT thread starter macrumors member

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    May 23, 2011
    #20
    Managed to find 2 working CPU's for my G5 on ebay for £7 so should have a fully working G5 pretty soon
     

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