Overheating G5 Core

[ftalbot]

Hi. I only used sporadically my Quad G5 in the last year. Last week, while I was compiling some stuff in Leopard, it suddenly turned off. At first, I thought it was power related : I have a Radeon x1900 and a Radeon 5770 GPUs (the second is for Linux) and I assumed they were drawing too much power despite the fact that one is always idle (the 5770 in Leopard and the x1900 in Linux). So far, I haven’t seen anything special in the logs, but upon checking the CPUs temperatures I realized that one core is clearly hotter than the others. A minute after startup, without any app launched except for the CPU and temperature monitors, I have the following temperatures :

• CPU A Core 1 : 35-40°
• CPU A Core 2 : 35-40°
• CPU B Core 1 : 45-55°
• CPU B Core 2 : 60-70+°

Can somebody advise me on what I should do to? I’m considering repasting the CPUs (a first for me with this kind of device), but I suspect I’ll have to do something more complex...

 

[CJRhoades]

I had the same issue with my Quad G5, one core being much hotter than the rest. A repaste didn’t help. It’s likely a clogged water block which would require taking apart and flushing the LCS. I’ve decided to convert it to air cooling instead.

 

[Macbookprodude]

Wait a second.. How can it be possible an ATI Radeon 5770 can be run under Leopard on a G5 Quad ? What is your secret, as I would like to run my 5770 in the G5 Quad. Also, I may add - what pump do you have ? Strange as it may seem, those G5 Quad owners who have the dual pump system - I am sorry to report 2 is not reliable.. I read the single pump is which I have. I have used my G5 Quad since 2008 and it still works great - though, I maybe retiring it, as it does use a lot of energy. I have a Mac Pro 5,1.

 

[Amethyst1]

How can it be possible an ATI Radeon 5770 can be run under Leopard on a G5 Quad ?

It's impossible. The OP has stated it's only for Linux.

 

[Macbookprodude]

It's impossible. The OP has stated it's only for Linux.

So, ok.. an Intel Mac graphics card can be run under Linux on a PowerPC machine ? Interesting.

 

[ftalbot]

I had the same issue with my Quad G5, one core being much hotter than the rest. A repaste didn’t help. It’s likely a clogged water block which would require taking apart and flushing the LCS. I’ve decided to convert it to air cooling instead.

I’ll have to look into this. You used dual core 2.3 heat sinks. Have you considered using heat sinks from older Power Macs G5? They are way easier to obtain.

Also, I may add - what pump do you have ? Strange as it may seem, those G5 Quad owners who have the dual pump system - I am sorry to report 2 is not reliable.. I read the single pump is which I have. I have used my G5 Quad since 2008 and it still works great - though, I maybe retiring it, as it does use a lot of energy. I have a Mac Pro 5,1.

It’s the single pump model.

 

[CJRhoades]

I’ll have to look into this. You used dual core 2.3 heat sinks. Have you considered using heat sinks from older Power Macs G5? They are way easier to obtain.

Older heatsinks are not compatible. Even if they were, I don’t believe they’d have enough cooling performance as they were only designed for single core chips.

 

[NikolaPPC]

I’ll have to look into this. You used dual core 2.3 heat sinks. Have you considered using heat sinks from older Power Macs G5? They are way easier to obtain.



It’s the single pump model.

If it is a single pump version, CPU B block is probably clogged. Disassembly and cleaning is needed if you want your LCS to last for many years!

Cheers, Nikola!

 

[Jubadub]

If it is a single pump version, CPU B block is probably clogged. Disassembly and cleaning is needed if you want your LCS to last for many years!

Cheers, Nikola!

Is there a very noob-friendly LCS cleaning/maintaining tutorial or write-up somewhere you know of?

 

[Macbookprodude]

Very strange, I have a single pump G5 Quad.. I will admit though i DON'T use it everyday which is probably why I never saw this issue with mine.

 

[ftalbot]

Is there a very noob-friendly LCS cleaning/maintaining tutorial or write-up somewhere you know of?

I don’t know if it counts as « noob friendly », but there is a very detailed guide from 2012.

 

[ftalbot]

Hi. A followup and another question... Before attempting to service my LCS, I got another used LCS + CPUs unit as a spare (which says a lot about my self-confidence).

I installed it in my Quad G5. I get the startup chime but the screen remains dark. After about five seconds, the red overtemp del on the motherboard turns on and the fans ramp up. The other diagnostic dels remain off. I reinstalled the unit to be sure and got the same behaviour. Each time, I turned the computer off pretty quickly after the fans went full speed. I've put the original unit back and everything is ok.

Could a sensor or the pump be damaged on the replacement unit? Should I wait longer when the fans run full speed?

Thanks!

 

[dorkshoei]

I don’t know if it counts as « noob friendly », but there is a very detailed guide from 2012.

I figured I'd add to this thread as this is already for the Quad G5 rather than starting another.

Two of my four cores are running hotter than the others at multiuser idle (39.1 39.2 63.2 67.5) and if I load the machine I get a critical temp warning and the machine abruptly powers off.

More disturbing as I detailed on this thread, I'm getting lockups in Open Firmware (the machine will lock up from a cold boot within 3 commands)

The above guide linked to by @ftalbot is for version 1 of the Quad CPU LCS (pictured below)

I have version 2 of the Quad CPU LCS (pictured below).

Does anyone know of any troubleshooting guides specific to version 2?

I disassembled the LCS and I don't have any leaks. Is there thermal paste that can be reapplied?

The only other potential issue I'm aware of is with the Northbridge chip which is on the underside of the PCB and there is a guide to diagnosing and applying new paste here.

I can't recall seeing any overtemp LED lit on the mainboard. Where is this LED?

Suggestions welcomed. Thanks!

Pics of my v2 LCS below:

 

[pc297]

Here are some guides to flushing the LCS.

PowerMac G5 Quad "The New Blood Mod" - A guide to flushing, modifying and refilling the dual-pump cooling system.

Hi all, this is a guide to my personal modifications to the Apple PowerMac G5 Quad rev.2 "dual-pump Delphi", pictured above. I will do my best to be thorough in my descriptions. Sadly I do not have pictures of my process in this version of the guide but I will be repeating this mod on another...

68kmla.org

G5 LCS refurbish and refill info - Apple Community

discussions.apple.com

I might have a go again myself, as my CPU B Core 2 is a tad higher than the other 3. I wonder if running ASD could help (but would definitely be needed after reseating the CPU and flushing the LCS)

Stupidly I had tried this before these instructions were out and ended up having to wreck the inlet shown on picture 4 above, if only I had had those instructions ?