Hi guys. This is my first post here, so forgive me if I sound like an idiot. :- I have a G4 Sawtooth that I popped a working dual 500 into, and the thing will work for a while and then it either freezes or goes into a kernel panic. I've tried swapping out RAM, video cards, hard drives, etc. just to eliminate the possibilities of an extraneous culprit. Firmware is up to date as well. But I think the processor is just overheating. The heat sink doesn't have those little pads on them, but I applied thermal paste at varying consistencies and have had varying degrees of uptime, but it inevitably locks up. Being ever resourceful, I put a second dual 500 I had laying around in and had the same result. So, I guess my question is, without those little pads on the heat sink, am I screwed? Does anyone know of a trick to keep the processors frigid? I was thinking about strapping another fan to the heat sink, but I hate to waste my time doing that if I'm missing something more obvious, or if that's just barking up the wrong tree. Maybe I could mod one of those little dorm refrigerators and slap the G4 in that. Fix it so when I hit the eject button on the keyboard it dispenses a cold beer while I'm reading my e-mail... ::)

In some cases, with earlier G4's, while they alll use snap-socket processors (I know, except MDD's) if the processor is too fast for the logic board, you'll get freezing or non-booting issues. Its not an issue of heat, but more speed. You might check your system console log to see if the system is writing the error to console, which would allow you to backtrace it.

I can think of a couple things you could check, first does your logicboard support dual processors? I think the early Sawtooth logic boards don't work with duals. Check your power supply, My dual sawtooth had panic problems and it turned out to be the power supply was faulty. Also the dual 500 in the gigabit had a higher rated Power supply than a sawtooth 330 watts compared to 235 for the sawtooth. You should remove the old pads from the heatsink, I would put on some artic silver. lastly check the panic log. hope this helps.

Unfortunately, I'm not too adept at deciphering these console logs, but I'll paste in the crash report, which is essentially what was in the panic log. I really don't think the motherboard is the issue, since this machine has run the Dual 500s before. My roommate is running dual 1.2's on what amounts to the same machine. I do know that after I pull the heat sink following a freeze, the thermal compound looks like it has little cracks in it, but I don't know if this is just the result of divorcing the sink from the card, or if it really is forming those cracks when it is up and running. If that's the case, I would imagine all the air spaces that would create would be more than enough to overheat it. Does anyone know if those thin pads Apple puts on the bottom of the sinks are an essential component? Any ideas as to a substitute if they are? The thermal grease idea doesn't seem to be working very well for me, but maybe I'm doing something just plain retarded too.
When I check the crash log I usually get something like this: Tue Jan 22 22:20:27 2008 crashdump[100]: crashdump invoked as panicdump
The last time it locked up it had the following on my screen after firing it back up in the "report to Apple" prompt:
panic(cpu 1 caller 0x000A4554): attempt to interlock mutex (0x0167B5B8) failed on mutex lock

Latest stack backtrace for cpu 1:
Backtrace:
0x000954F8 0x00095A10 0x00026898 0x000A4554 0x000228F8 0x000ABEAC 0x19636F6D
Proceeding back via exception chain:
Exception state (sv=0x25F5F280)
PC=0x9000B348; MSR=0x0200F030; DAR=0x0507AEC0; DSISR=0x0A000000; LR=0x9000B29C; R1=0xF00FD630; XCP=0x00000030 (0xC00 - System call)

Kernel version:
Darwin Kernel Version 8.11.0: Wed Oct 10 18:26:00 PDT 2007; root:xnu-792.24.17~1/RELEASE_PPC
Model: PowerMac3,1, BootROM 4.2.8f1, 2 processors, PowerPC G4 (2.9), 500 MHz, 768 MB
Graphics: ATY,Rage128Pro, ATY,Rage128Pro, AGP, 16 MB
Memory Module: DIMM0/J21, 128 MB, SDRAM, PC100-222S
Memory Module: DIMM1/J22, 128 MB, SDRAM, PC100-222S
Memory Module: DIMM2/J23, 256 MB, SDRAM, PC100-222S
Memory Module: DIMM3/J24, 256 MB, SDRAM, PC133-333
Network Service: Built-in Ethernet, Ethernet, en0
PCI Card: pci1106,3038, sppci_usbuniversal, SLOT-C
PCI Card: pci1106,3038, sppci_usbuniversal, SLOT-C
PCI Card: pci1106,3104, SLOT-C
Parallel ATA Device: WDC WD200BB-00CFC0, 18.64 GB
Parallel ATA Device: WDC WD200BB-53AUA1, 18.64 GB
Parallel ATA Device: PIONEER DVD-RW DVR-108
Parallel ATA Device: IOMEGA ZIP 100 ATAPI
USB Device: Logitech USB Keyboard, Logitech, Up to 1.5 Mb/sec, 500 mA
USB Device: Apple Optical USB Mouse, Logitech, Up to 1.5 Mb/sec, 500 mA

Like I said, I'm not great at reading these things. About all I can do is look at them and hope something will jump out as an "ah ha!" moment, but that hasn't happened yet. Maybe one of you can glean a little more info from it than I can. Thanks! (And I did run a freeware utility which confirms the machine is dual processor capable).

The only useful thing I can pull from there is the term 'CPU'.
You need a copy of Mac Test Pro. Or maybe Techtool.

Thanx. I haven't used either of those apps, but my assumption is that they'll be useful in tracking down hardware issues? I think I blew holes in my overheating theory tonight, at least to a certain extent. I slapped two fans in the machine (one aimed directly in to the fins of the heat sink and another blowing across the fins) and another fresh air intake fan in the spare PCI slots, making it cool as a cucumber inside and it still locked up. But the difference this time is it ran for almost an hour at idle speed before it seized on me. Previously, it would make it maybe 5 to 10 minutes, tops. So, running cooler, I did manage to coax more uptime out of it, but it still eventually locked. Another thing that keeps me coming back to the heat theory is that it won't boot right back up after a freeze, but if I wait 5 or 10 minutes, it boots again, but the uptime is much shorter; kind of like it hadn't had the opportunity to cool completely, thus heating to failure more rapidly the second time around. I put the 400 back in it, before tonight's internal hurricane experiment, and ran the system load app at 90% for over three hours, and then left it on for almost 24 hours running a processor hog of a screen saver and it just hummed along all day long with nary a care. I think that might help rule out things like bad RAM, but an earlier suggestion of a weak power supply could still hold merit, if the dual 500 is a significantly greater power hog than the 400. I'll see if I can lay my hands on the apps you suggested and see if they bear any fruit. I may have to consign the machine to being a simple 400 MHz unit if I can't figure this out.

In newer machines, the system log reports shutdown causes and overheating issues. Worth a look but those things have far fewer sensors.

Yeah, the machine's sensors are pretty few. My G5 at work has all kinds of info available. Alas, the sawtooth is bereft of many modern bells and whistles. I'll have to give TechTools a run for the money and see what else I can find as I delve ever deeper. I'll keep you posted.