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PowerMac G5: What's your U3/Memory Controller Heatsink temp?

Discussion in 'PowerPC Macs' started by JoeG4, Feb 4, 2011.

  1. macrumors 68020


    Hey guys, I just picked up a G5, runs great but I've noticed the memory controller heatsink is pretty darn toasty (currently around 150f/67C when idle). If I push it, it gets up to around 70c and then cools back down into the 60s.

    It does worry me, but it appears to be stable. The processors are running really cool at 113-125f!

    Anyone else? :) Thanks
  2. macrumors 601


    I know mine is/was usually higher, usually around 130-150*F and I believe that's under load. You can try dusting all the dust out with a can of compressed air. Those temps are pretty high for idle though so cleaning the dust out would be my first approach.
  3. macrumors 68020


    lol I'm wondering why I haven't tried the compressed air approach.. I guess because I never have any sitting around.

    I was just planning on yanking the board out (just haven't yet). Thanks for the advice :)
  4. macrumors 601


    It's much more convenient if you have an air compressor :D

    Never have to buy those expensive cans again and you get much much more air pressure too.

    Just watch out for the fans as you don't want to overspin them. You can damage the bearings or they can self destruct and explode pieces of plastic everywhere. It's best to put something in the fan to keep it from spinning when cleaning them.
  5. macrumors 68020


    It turned out that one of the plastic retaining clips had come off, so maybe 1/2 or 1/4 of the heatsink was actually touching the memory controller. Since there's no temperature probes near it, I'm fairly confident that when you see "U3 memory controller" or "memory controller heatsink" temps, that's coming from the chip itself.

    It also turns out, that this sort of thing kills a lot of G5s, so if you have a high U3 temp.. look into fixing it!

    Now, I need to figure out what to replace the darn clip with! I'm thinking nylon nuts & bolts. :D One thing that caught me as strikingly odd was the grey thermal compound - I've NEVER seen that in an Apple product before and am beginning to wonder if someone tried to "fix" the problem (heheh). Maybe they did that? Doesn't seem a very Apple thing. It was, however applied in the typic Apple fashion (extremely overapplied!)
  6. macrumors 68020


    So I fixed the heatsink, but the temps still suck. It's not in the 70s, but it's in the mid-high 60s.
  7. macrumors newbie

    I just bought an old G5 1.9ghz 17" and yes the memory controller can get around 72c, I changed the thermal paste but it is still getting hot.
  8. macrumors 68020


    Meh, I'm going to run it into the ground. The worst that can happen is the motherboard craps out and I sell the machine off for parts and get my $50 back. Whatever.
  9. macrumors member

    Here are some screen shots of my recently repaired Dual 2.5.

    G5 LCS repair-screen shot of raw processing.jpg

    G5 repair screen shot-LR export.png

    One shot is when the machine is under load (Photo with no text added) and when the machine is at idle.

    I have a full thread on my LCS Repair, which talks some about CPU temps, but is mostly about the repair its self. You might find it useful.


    Good luck,
  10. macrumors 68020


    Thanks for sharing that ^^

    I ended up yanking the little blower fan off of its duct (literally, it's held on with rubber thingies and if you pull at it properly it'll just pop off and you're good to go), and have it (almost) hanging next to the video card atm.

    Meanwhile, a (not ducted!) regular 80mm antec is in its place and with a light load, the temps are at a much more sane 60c. Even at heavy load, the highest I've seen is 64c so there's some good going on there.

    With a proper ducting setup (will get around to it soon), I expect that to drop down into the 50s ^^ Glad to see that's.. somewhat reasonable ^_^
  11. macrumors 65816



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  12. macrumors 6502

    Mine stays around 128 fahrenheit.
    I thought that was high, but it seems several others on here have temperatures even higher than mine.

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