What a bad G5 CPU can look like

[PowerHarryG4]

I don't know if you'll find this interesting or maybe you already knew this, but I definitely found this interesting. So I recently purchased a 2005 DP 2.0 powermac G5. I've been having lots of fun with it, photoshop, web-surfing and some gaming, etc. The only problem is one cpu would get ridiculously hotter than the other - up to 75 degrees Celsius, when the other was at a cool 53, barely breaking a sweat, even when both CPUs were being utilized. This made CPU B fans go crazy, full blast when loading websites, for example. I just assumed this was normal behaviour because the machine ran perfectly fine with zero stability issues - everything felt pretty fast.

After it bothering me a lot, I put a copy of Apple Hardware Test all in one on a disc and booted ASD 2.5.8 to do a thermal test. CPU A failed with an error of 'Tafs out of range replace CPU'. So I went on ebay and found a replacement cpu, which was two CPUs for £20 pounds if your curious (i'll just keep one CPU spare for now). I replaced the thermal compound on the new cpu and the one in the machine and re-ran the thermal test and both CPUS passed fine. Now when doing running the same type of application as before, such as photoshop the fans hardly ever ramp up and I also haven't seen either CPU go past 67 degrees.

So to sum up, this post was just to show that a bad CPU doesn't always mean stability issues or obvious problems. It can also mean a cpu which simply gets really hot.

Edit: typo, it was CPU B that failed in the thermal test, not CPU A

Before CPU replacement (i know it's not the same application running, but you can still see the difference in temperature)

After CPU replacement

 

[B S Magnet]

I don't know if you'll find this interesting or maybe you already knew this, but I definitely found this interesting. So I recently purchased a 2005 DP 2.0 powermac G5. I've been having lots of fun with it, photoshop, web-surfing and some gaming, etc. The only problem is one cpu would get ridiculously hotter than the other - up to 75 degrees Celsius, when the other was at a cool 53, barely breaking a sweat, even when both CPUs were being utilized. This made CPU B fans go crazy, full blast when loading websites, for example. I just assumed this was normal behaviour because the machine ran perfectly fine with zero stability issues - everything felt pretty fast.

After it bothering me a lot, I put a copy of Apple Hardware Test all in one on a disc and booted ASD 2.5.8 to do a thermal test. CPU A failed with an error of 'Tafs out of range replace CPU'. So I went on ebay and found a replacement cpu, which was two CPUs for £20 pounds if your curious (i'll just keep one CPU spare for now). I replaced the thermal compound on the new cpu and the one in the machine and re-ran the thermal test and both CPUS passed fine. Now when doing running the same type of application as before, such as photoshop the fans hardly ever ramp up and I also haven't seen either CPU go past 67 degrees.

So to sum up, this post was just to show that a bad CPU doesn't always mean stability issues or obvious problems. It can also mean a cpu which simply gets really hot.


View attachment 1750836
Before CPU replacement (i know it's not the same application running, but you can still see the difference in temperature)

View attachment 1750826
After CPU replacement

Wow, your U3 Heatsink runs ice-cold (which unfortunately, mine does not, even after a comprehensive cleaning of everything and new thermal paste last December). Mine always hovers between 67 and 76°C:

Currently the setup is running Icecast and a couple of plug-ins for that. Anything much more and I get the CPU Alignment kernel panics.

What surprises me is how AHT 2.5.8 cited CPU A as being faulty, even thought it was running much cooler than CPU B. I honestly would have expected CPU B was on the way out there.

 

[PowerHarryG4]

Wow, your U3 Heatsink runs ice-cold (which unfortunately, mine does not, even after a comprehensive cleaning of everything and new thermal paste last December). Mine always hovers between 67 and 76°C:

View attachment 1750846

Currently the setup is running Icecast and a couple of plug-ins for that. Anything much more and I get the CPU Alignment kernel panics.

What surprises me is how AHT 2.5.8 cited CPU A as being faulty, even thought it was running much cooler than CPU B. I honestly would have expected CPU B was on the way out there.

Oops that's a typo on my part. It was CPU B that failed not CPU A. I never knew the U3 heatsink was one to look out for, i'll keep that in mind in looking at the temps and also check out Icecast if need be, i hadn't heard of that.

 

[ax81]

Yes, silicon ic circuits degrade with age and tend to run hotter. I've seen this behaviour on the pc with several gpus. As for mac ppc CPUs, your issue seems quite curious, since the datasheet for 970MP for instance, lists them as rated for maximum operational temps of 105 degrees C and temps in the 60-80 range would seem completely normal. My own recent experience also suggests something along similar lines, as I've been unlucky enough to purchase a G5 Quad with a clogged liquid cooler and the B CPU would idle at ~60C and then hit 100C within ~5 minutes of running any intense app causing a forced stand by mode. I ended up removing one of the CPUs and moving the B cpu into the A socket, just to verify that it wasn't in fact a cpu going bad and guess what, the single dual core CPU temps are fine now (no wonder). At no point however have I encountered any stability issues, even though the cpu was running at 90-100 degrees C for days before I managed to figure this out.

 

[B S Magnet]

Oops that's a typo on my part. It was CPU B that failed not CPU A. I never knew the U3 heatsink was one to look out for, i'll keep that in mind in looking at the temps and also check out Icecast if need be, i hadn't heard of that.

Yeah, your memory controller is running nice and cool, which is nice.

Mine is on the way out.