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Level 1

11 points

PowerMac G5 Dual 2GHz freezes any time, boots sometimes with one processor

Since two weeks I experience freezes at different up-and-runnng time. It could happen at grey startup screen (after a while fan goes wild), could be after some minutes working in a full booted user environment.

I run AHT several times, no error reported. When I took out all RAM except for Apple RAM, it still freezes at some time.

Now, by random, my machine starts sometime with only one processor and is stable for hours (only the fan runs higher and cpu load is most of the time near 100 percent). Activity shows one bar only, System Info says: Number of CPUs=1. I have no idea which processor runs and which "sleeps" deadly. iStat tells only about CPU A as having a temperature, the fans of CPU A run higher, but the fans of CPU B run also on a lower level.

The "U3 Heatsink" reads 65-70 degree Celsius. Is that (too) high?

Only once I got a kernel panic during verbose startup. It read:
"System failure: cpu=1; code =00000001 (corrupt stack)
unalined fram address: 0x00000001"

I am tempted to shut down one CPU with Open Firmware command, but will it be the defect one? At least the machine is doing something regular then, but is slow...

Any help is much welcome!
Yours, Whoopy

G5 dual 2GHz and G4 Titanium, Mac OS X (10.4.6)

Posted on Aug 20, 2008 4:59 AM

200 replies

NiqueT

Level 1

0 points

Oct 18, 2010 8:00 AM in response to BDAqua

Greetings BDAqua!

That was quick - thanks for the suggestions! I had tried re-seating both processors several times over the weekend, but hadn't given RAM re-seating/tweaking a try yet.

Unfortunately, no luck with shifting the RAM slightly outward. I wonder in general that re-seating the RAM might work for some people as it puts pressure on that "sensitive" area of the logic board near where the U3 chip resides, and so might get a bad solder joint beneath the chip to reconnect for a while. (I thought about going so far as to rigging a spring between the back (non-opening) cover and heat sink that covers the U3 chip on the flip side of the logic board; the constant pressure might keep any bad solder joints in contact with the logic board itself!).

The system still seems quite stable once booted into the "metastable" one-processor-reported state, as long as I don't shut down! The hairdryer method is the only way to get both processors reported, though the system crashes shortly thereafter anyhow. It would be great to get the system stable in this latter case, but even on just one processor the computer accomplishes a good deal 🙂

Thanks again!
Nick

BDAqua

Level 10

239,333 points

Oct 18, 2010 1:48 PM in response to NiqueT

I think I'd stick with one CPU, did you try using CHUD Tool's Proccessor Pref Pane to disable the second one?

NiqueT

Level 1

0 points

Oct 18, 2010 2:50 PM in response to BDAqua

Agreed - one processor is better than a completely non-working system!

I did experiment with disabling the second processor via command line in the OS, as well as in the open firmware environment prior to the boot sequence using

setenv boot-args cpus=1

In both cases, it didn't stop the hanging boots 😟. To your knowledge, does this command do the same thing as tweaks made via the CHUD Processor Pane?

(I installed the CHUD Processor Pane just now for kicks. Since the system only "sees" one CPU on this boot, there's no option to disable the second one. So I think to do it via this tool I'd need to get the logic board heated up with the hairdryer so that it's stable enough to boot the OS and recognize both CPUs, disable the second CPU via the preference pane, and then shut down. Not so easy!)

Thanks again!

BDAqua

Level 10

239,333 points

Oct 18, 2010 3:09 PM in response to NiqueT

To your knowledge, does this command do the same thing as tweaks made via the CHUD Processor Pane?

I think it does, but I don't think I've ever seen commands to turn off the Caches.

Since the system only "sees" one CPU on this boot

Is that maybe with cpus=1 maybe?

NiqueT

Level 1

0 points

Oct 18, 2010 3:33 PM in response to BDAqua

That's a good point about the cache, and would certainly be a reason to try the CHUD tool over the command-line technique. I may give it a go later this evening.

The current value of "cpus" is "2", so it's definitely the logic board issue that is preventing the OS (and thus the CHUD tool) from seeing the second processor in this current boot session.

PowerMac G5 Dual 2GHz freezes any time, boots sometimes with one processor