Cannot pass Apple Service Diagnostic 2.6.3 Thermal Calibration on my Power Mac Quad G5

[Tazintosh]

Hi folks,

I recently got a Power Mac G5 2.5 GHz already max out to 16 GB of ram and with a FX 4500 for… 30€

It took a loooo…oong time to clean it all but I finally own a shiny almost brand new PM G5. I've done:

• Full disassembly and OceanGate Titan Deep Clean Level mainly with isopropyl alcohol and air compressor.
• Changed all thermal paste and pads for: logicboard backside, video card, CPUs (thin layer of MX-6).
• Full clean and refill of the Liquid Cooling System (version 1): multiple pass of 80°C pure vinegar into the radiator, rinse, refill with auto green coolant, removing as much bubbles as possible (nightmare). Pump is perfectly working and finger test while using a heat gun is astonishing.

All is fully working and running 10.5.8. The computer is stable under load, running 4 instances of yes > /dev/null & for more 1 hour already (at the time of this writing).

Running ASD 2.6.3, all tests have successfully passed (takes more than 5h for 16 GB of ram), but Thermal Calibration is for now always failing with error for both CPUs

ERROR CPU0 - Processor Max. temperature exceeded

Reseat processor and retest unit. Replace processor if it continues to fail.

ERROR CPU1 - Processor Max. temperature exceeded

Reseat processor and retest unit. Replace processor if it continues to fail.

You'll find attached two captures of the screen with no load and under heavy load (> 1h).

I feel my temperatures are fine:

• At rest:
  • CUPA ≈ 35° C
  • CPUB ≈ 45° C
• Under >1h heavy load:
  • CUPA ≈ 55° C
  • CPUB ≈ 75° C

Two questions only:

1. Why there is always a temperature difference between A and B? (I've seen this online many times). In my case: ≈ 10°C between A & B at rest and ≈ 20°C under heavy load.
2. Why the thermal calibration is failing for "Processor Max. temperature exceeded" considering the CPUs under load seems absolutely stables? (All tries have been run with —all— covers)

Thanks a lot in advance for your inputs.

 

[Doq]

1. Why there is always a temperature difference between A and B? (I've seen this online many times). In my case: ≈ 10°C between A & B at rest and ≈ 20°C under heavy load.

Could be any number of factors, but the most common are either "user error" or "that's just how it is". CPUs are never created truly equal. While both could perform identically, one of the CPUs may generate more heat than the other and that's just how it is.

I don't have a Quad (wish I could find one without having to defer my rent and not buying food), but I do have a dual-proc PC and one of the otherwise identical CPUs runs noticeably hotter than the other.

I don't know about thermal calibration. I would just omit doing it but I'm not sure if something bad happens if you don't.

 

[Tazintosh]

Thanks for the answer @Doq.
Following your thought, switching CPU should then switch temp difference between A & B placement.
But what surprised me initially was precisely because over my web searches, I was actually always finding people with A cooler than B.

 

[Tazintosh]

Something new and weird happened today:
After two weeks at least not using it (basically since my above photos), I've turned on the G5 for a curious and interested friend.
Initial temperatures for CPUs were good, around 35°C has screened on my initial post.
Then, the CPUB temp started to slowly rise up (without any noticeable load).
It ended up to 98° and the G5 put itself in sleep mode but also hang.
Both led "Overtemp" and "Checkstop" were lit.

I let it rest many hours and did the test multiple times, but the behaviour remains the same --> Both led "Overtemp" and "Checkstop" ends up being lit.

I would be extremely surprised if something were wrong with my thermal compound application, specially since I stress tested initially the G5 during 1h 20 min. But before unmounting all, what's your opinion on this guys ?

 

[Tazintosh]

Quick Update.
I might have found a culprit. At least I think I've to deeply investigate on this direction:
I noticed that since yesterday tests, the G5 was going "Overtemp" quicker and quicker.
Even this morning, while the machine was cold, it took less than a minute to trigger the both led "Overtemp" and "Checkstop" leds.
I've unmounted the LCS with processors, looked closely to the tubes while shaking and found many particules floating around.
My guess is that the small inlet filters are clogged. The new liquid might have helped detaching some deposit and while the system was perfectly clean hours after refilling and testing, those passing weeks may have been sufficient to built enough amount to clog the filters. And the more I was trying yesterday, the more the pump was pushing debris to the filters.
I'll probably buy an ultrasonic cleaner and make a new cleaning. Looks like mine was not good enough.

 

[ToniCH]

I've unmounted the LCS with processors, looked closely to the tubes while shaking and found many particules floating around.
My guess is that the small inlet filters are clogged. The new liquid might have helped detaching some deposit and while the system was perfectly clean hours after refilling and testing, those passing weeks may have been sufficient to built enough amount to clog the filters. And the more I was trying yesterday, the more the pump was pushing debris to the filters.
I'll probably buy an ultrasonic cleaner and make a new cleaning. Looks like mine was not good enough.

Yes, dirt coming unlodged inside the radiator could very well cause all kinds of trouble with coolant flow. After reading many of these LCS threads on various forums one common thing is that the radiator is super difficult to get properly cleaned. People needed to do it many many times before they can be sure all the crud is really out.

And then come the air bleeding troubles. I've seen people use all kinds of contraptions to help bleed air out, even vacuum pumps.

I have a 6ltr ultrasonic, I hope the thing fits into it when I start to rebuild mine. Can you please roughly measure the outer dimensions on your radiator?

 

[Tazintosh]

I have a 6ltr ultrasonic, I hope the thing fits into it when I start to rebuild mine. Can you please roughly measure the outer dimensions on your radiator?

The "Bouding Box" of the piece (radiator + CPUs boards support) would be ≈ 20.5 x 18 x 14 cm
20.5 being the CPUs boards support, which belongs to the assembly.
The radiator itself is ≈ 18 x 14 x 5 cm

 

[ToniCH]

The "Bouding Box" of the piece (radiator + CPUs boards support) would be ≈ 20.5 x 18 x 14 cm
20.5 being the CPUs boards support, which belongs to the assembly.
The radiator itself is ≈ 18 x 14 x 5 cm

Thanks! If one can separate the radiator from the supports then it would fit completely submerged as the tank is 30 x 15 x 15 cm. How is the thing put together? From pics it looks like there are screws?

But, I would say this size for an ultrasonic is pretty much smallest I can recommend for general use. When I bought it few years ago I thought 6ltrs is plenty but In retrospect I would probably buy a 10ltr or even little bigger if I was looking for one now.

 

[Tazintosh]

I'll go for a 15L personally (not for this, but for other projects too).
I'm not sure you care about cleaning the support plate. If the radiator itself is fully merged, you're good no?

 

[ToniCH]

Sure, 15L would probably be good if you do some car/bike/small engine etc. stuff too.

Yeah, no need to get the sheet metal ultra clean!