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TitaniumFrog

macrumors newbie
Original poster
Jul 24, 2021
28
14
So I recently acquired a 2.3DC G5 which at first POSTed to memory errors - as it turns out, the previous owner put incompatible memory in the machine. So yay, €30 for a complete machine, original HDDs and all.

The machine doesn't run too hot in idle, but it goes up quickly when I load up the CPU. It's also pretty noisy in general, so I think it's due for a repaste and thermal calibration. I have ASD 2.6.3 here handy after my Quad adventures. Given that the U3 is known to run hot as well, I want to inspect and clean the entire machine, being extra vigilant when looking for bulging caps. Logic board out and all. An FX 4500 (proper PowerPC version) will be revised as well.

As far as I know, there are no thermal pads on a 2.3DC, just thermal paste. The FX 4500 does use thermal pads for the memory and if memory serves me right, they're 2mm thick. Can anyone confirm that?

In doing a full overhaul, I want to repaste the CPU and the U3. Not sure about the two heatsinks inbetween the RAM banks, I may keep them there.

I've read https://forums.macrumors.com/threads/power-mac-g5-dust-out-and-thermal-paste-re-do.2097720/ (thanks AphoticD!) and done some Googling myself as to what would be the best solution for thermal compound. I see two options: the easy one is getting a tube of high quality thermal paste like Noctua's NT-H2 or Thermal Grizzly Duronaut (source) and the hard one is getting something like Honeywell PTM7950.

I'm not sure which of the two I would take. PTM7950 seems to be the be-all-end-all for direct die cooling, but it's pretty difficult to work with and it's not that well available here (and I don't really trust the AliExpress prices). Thermal paste is way more convenient, but it may perform less than the PTM stuff would. Regarding the thermal pads, I was think some Gelid stuff to do the trick.

Is the PTM7950 stuff really the way to go, or is that overkill? Reaching U3 for a repaste is a pain ;)

And a side question: I'm trying to get 1920x1200 out of the FX 4500 (converted to HDMI, no DVI displays available...), but it either shows me 1920x1080 (which works) or 1920x1440 (which is garbled). 1920x1200 is not in the list in either Leopard or Tiger. Any tips? It's a 2560x1440 panel.
 
I'd give SwitchResX v4.1.6 a shot.

Ive not used PTM7950 but did use arctic silver 5 for my PMG5s a few years back and they are running great temps. I get with how much of a PITA it is to get at the U3, you are looking for the best staying power there. Again I used what I had at the time and it is working great for me. Hopefully someone has some experience with and opinion on the PTM7950.

I did go ahead and ask LegacyAI what they thought and they stated that they agreee that PTM7950 lasts significantly longer because of its phase change material composition, so is a good choice for hard to reach areas that will have longer duration between servcing.
 
We're a month further in time and space, but it's all done!
  • New thermal pads on the Quadro FX 4500. You will need 1mm thick pads, I used Gelid Extreme. One stick of 120x20x1.0mm was enough for me, but YMMV. A duo pack isn't a bad idea in this case.
  • Used Honeywell PTM7950 from RGeek Flagship Store on AliExpress (https://nl.aliexpress.com/item/1005004870180057.html) for the die. This is the PTM-stuff I used for the rest of the build as well.
  • Used Noctua NT-H2 for the South Bridge I/O device and disk controller (underneath the relatively small black heatsink at the front of the logic board).
  • Used the PTM for the North Bridge memory controller and PCI bus bridge. Those nylon clamps are proper disaster -_-
  • Used the PTM for the processor as well.
And then the usual when you strip a G5:
  • Removed any and all fans and cleaned them
  • Removed dust from the logic board where necessary
  • Removed dust from the tower cooler where necessary
  • Cleaned all I/O ports
  • Removed the PSU. Cleaned the fans and then opened it up to remove all dust inside of it.
  • Replaced the top HDD with an SSD, kept the HDD because I like the clicky noises...
  • Made sure to give it a full bank of RAM (16GB usable, gorgeous!)
Result: the beast now idles at 30 degrees C on the CPU. 40 degrees C on U3 and about the same on the GPU core. CPU intake/outtake runs at approx 500 rpm, drive bay and backside at 1000 rpm and slots intake at 1500 rpm. When pegging the CPU at 100%, it doesn't exceed 50 degrees C. ASD passed all the normal checks and thermal calibration was no issue either. Time to grab myself another SSD and install Debian on this thing :)
 
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