[ygddrasill]

Hi everybody,

I recently was given an old 2x1.8Ghz PPC G5 in order to build a personnal server but I have troubleshooting with CPU's temps that are really too hot (75°C with no app open, only Finder).

I know these temps are not that "hot" but I can't imagine what it would be when I'll open Safari, iGetter, iTunes, CyberDuck, Adium and Photoshop CS4...).

I first unmount everything, blown inside some bottled air to make sure there were no dust creating overheating inside and remount everything.

Installed Leopard (last OS installable on PPC machines), made the last updates possible and restart.

Everything is working well althought this CPU's temp is so damn high and fans's speed are still at 300rpm. I was looking for some app that would do the same as SmcFanControl for Intel based Macs but for PPC's ones.

After many internet searches on many forums I finally admitted there were no software able to set fans's speed, the only way was manually editing the AppleFan.kext integer's values.

WhatI did, reducing the integer values to lower rates (256x multiples), then restarted the Mac but nothing happens. As I check the changed values, they indeed are the ones I edited but the fans still are at 300 rpm and the CPU's temp 75°C...

Does somebody have any solution for that issue, I feel I checked everything that was possible but nothing seems to work.

Any help is welcome...

Ygddrasill

[ChrisF]

G5s run hot. Do the fans cycle faster under load? If so, don't worry about it.

[ygddrasill]

Hi ChrisF,

thanks for your answer, I know G5 do run hot but no, the fan's cycle doesn't faster under load, that's my problem. I'd like them to run faster to cool the G5 down, and I don't care about noise, I'd like my G5 to work corrctly.
Because of the heat it works like if 25 apps were loading.

Any clue?

[OreoCookie]

The fans are controlled by the system and even on Intel-based Macs, smcfancontrol can only increase the minimum rpm. To the best of my knowledge, there is no such tool for G5s. There is, however, an Apple firmware update that addresses fan issues on some G5s. I suggest you don't muck with it unless you're having problems, i. e. when your system is unstable and crashes under load. The system controller should regulate the rpms of the various fans according to what is necessary for safe operation of your G5.

[Big Mac]

G5s may run relatively hot, but the OP is right to the extent that 75°C for a CPU is way, way too hot. I frankly don't trust that temperature reading because that's substantially hotter than I've ever seen my G5 DP 2.0's processors run at. I think 75 C is much hotter than they could possibly be rated to run at, so I just don't trust those readings. The only component in my G5 that runs near that temperature is the U3 memory controller.

Chris, if you boot into single user mode and leave it sitting at the prompt for a few minutes do the fans eventually rev up to full blast? If they do then I'd assume there's no fan issue. Have you run the Hardware Test disc?

If your Mac runs fine under load and the fans go higher when needed, then obviously it's a problem with a temperature sensor or the software you're using to read the values.

[ChrisF]

Originally Posted by Big Mac 

Chris, if you boot into single user mode and leave it sitting at the prompt for a few minutes do the fans eventually rev up to full blast? If they do then I'd assume there's no fan issue. Have you run the Hardware Test disc?

I'm not the one with a G5, I've long since sworn off PPC machines.

[Big Mac]

Sorry for the mix up, Chris. I've been up all night working, so I'm fatigued and not devoting full attention to my replies.

[Waragainstsleep]

75C is not going to be over the CPU max rating. It is still pretty hot though. You might consider getting some arctic silver to replace the thermal compound between CPU and heat sink but rebuilding G5 CPU modules is a pain and I don't recommend touching them unless absolutely necessary. If you want to run the fans quicker, pull the plastic baffler out. They should immediately speed up when you do. If they don't, something isn't working right.
You will notice there is a silver sticker on one of the tabs on the bottom of the baffler. If you remove that, you should be able to replace the baffler and keep the fans running full blast.

Speeding up the fans is really not the ideal way to fix this issue, since its not a proper fix. You should be trying to find the root cause of the high temp. Dried out thermal paste or some other bad contact between chip and heat sink is more likely. Like I say however, messing with the CPU modules can cause more harm than good. It is worth your while tightening the bolts that secure them to the board though. I've seen that fix all sorts.
Apple hardware test would be a good idea first. It should flag faulty sensors for a start.