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Jackdown_101

macrumors member
Original poster
Feb 28, 2017
40
5
Hi All,

I know that this is something that is generally addressed but I wanted to ask about my situation specifically.

I have recently upgraded the CPU's in a dual processor Mac Pro 4,1 flashed to 5,1 to the X5690's. I have used delidded processors for this.

It is only my second go at anything like this, applying thermal paste etc and I feel that I may already know the answers.......

The Mac has been running fine doing day to day tasks, browsing, spreadsheets, presentations, very light gaming, editing and video playback for a few weeks now. Resting Temps are always around

CPU A Diode 40/45
CPU A Heatsink 35/40
CPU A Core 45

CPU B Diode 35/40
CPU B Heatsink 30/40
CPU B Core 31

All fans running normally

Recently ran some video encodes and the core/diode temps ran up to 89 - 95 and obviously all the fans kicked in.

Is this a Thermal Paste/Heat Sink reattachment issue and am I best off cleaning down and reapplying? I'm also slightly concerned that I've now lost my recommended heat sink screw tensions for reattaching.

For novice thermal pasters like myself are thermal pads recommended at all or so they run too thick for delidded CPUs leading to issues akin to when you use lidded ones?

Any thoughts or advice welcome.

Thanks again for all the help here.

Currently not running open core, am booting off an NVME and running an RX470 8GB
 

carylee2002

macrumors regular
Jul 27, 2008
242
65
I personally use Arctic Silver for my thermal paste, I clean all the previous paste clean with alcohol then start over then prime the cpu with AS to fill in the gaps before applying a small amount of AS to the die. Then when the heat sink meets the CPU it will naturally spread. Then it will usually take many hours running your rig for everything to settle and then temps will stablilize over time. I've used this product for years back in the pc building days and it has never failed me. As for your stated temps I wouldn't be of concern since your are running a high cpu workload, as long as your everyday temps is running as 35-50c in normal you should be fine.
 
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KeesMacPro

macrumors 65816
Nov 7, 2019
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Arctic Silver is still my favourite too.
You could take a look at the AS site , there are tutorials about how to apply it correctly.

When the CPU Temps peak that high, I'd take a look at the NorthBridge diode T too.
Since you can tell the Temps, I suppose you installed MacsFanControl or iStats or so.

You could set the fans like this , to stay on the save side under any load:
Intake fan: sensor: NorthBridge diode , min T = 55 Celsius max T= 80 Celsius
Boost A fan: sensor: NorthBridge diode min T= 55 C , max T = 75 Celsius
All other fans can be left to "auto".
The NB and CPU A will be controlled simultaneously , as they share the same airflow (Boost A fan) and normally are the hottest parts .

There's a lot written here about how to set the fans, and many might think different about details, but from my own experience , as described above is the most effective setup for your fans without too much noise and keeping the whole CPU compartment quite cool.
Generally the DUAL CPU MP , compared to the single CPU MP, runs hotter.

BTW: a thermal pad for the CPU is not a good idea.
 
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Jackdown_101

macrumors member
Original poster
Feb 28, 2017
40
5
Thanks everyone.

When I replaced the CPUs I put new Northbrigde clips on and redid the thermal pate on that too.

Ran a Cinebench again and Northbridge temp seems stable around the 65 degree mark at all times. Even when CPU's under load.

Noticed the heat sinks don't warm up much in Mac Fan Control monitoring when the CPU's head on up towards 90/95 degrees. Think I'll re-paste with the recommended paste and see what happens.

Except the graphite thermal pad

Was thinking of the graphite pads yes. Although it seems that everyone else has had the same thought recently as the medium sized Thermal Grizzly ones are all sold out everywhere in the UK at the moment.....
 
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KeesMacPro

macrumors 65816
Nov 7, 2019
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Except the graphite thermal pad
Thx, didnt know that, although personally I think a thermal paste for the CPU will be superior.

Was thinking of the graphite pads yes. Although it seems that everyone else has had the same thought recently as the medium sized Thermal Grizzly ones are all sold out everywhere in the UK at the moment.....
The Graphite pad is extremely thin and not from Thermal Grizzly but from Innovative Cooling .
There is a Thermal Grizzly pad though that's very thin too its the "carbonaut" (0.2mm if i remember correct).
 

h9826790

macrumors P6
Apr 3, 2014
16,628
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Hong Kong
Thx, didnt know that, although personally I think a thermal paste for the CPU will be superior.


The Graphite pad is extremely thin and not from Thermal Grizzly but from Innovative Cooling .
There is a Thermal Grizzly pad though that's very thin too its the "carbonaut" (0.2mm if i remember correct).
The graphite pad should be the “easiest the apply”, and “hardest to go wrong” solution. And it has very high performance, basically same as the high end silicon base thermal paste.

My Radeon VII shipped with graphite pad rather than the normal thermal paste from factory. Even I replace that by liquid metal, the temperature improvement is just about 3°C (usually I can get 10-15°C improvement from thermal paste to liquid metal).

I personally very OK to use liquid metal, and know how to prevent accident. But if not, my second choice will be graphite pad now. Especially I know that's re-usable. And it won't "dry up".
 

Jackdown_101

macrumors member
Original poster
Feb 28, 2017
40
5
Overall should I be concerned by 99 degree temps on the processors when running, for example, Cinebench
Temps drop very quickly as soon as the process is complete.
 

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h9826790

macrumors P6
Apr 3, 2014
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Overall should I be concerned by 99 degree temps on the processors when running, for example, Cinebench
Temps drop very quickly as soon as the process is complete.
That 99 is not a problem. You can ignore that number. It means nothing on the cMP.

HOWEVER, your CPU's cooling is very very bad. Only very little heat can transfer to the heatsink.

You should NOT stress the CPU anymore until you fix the thermal paste / heatsink contact.

If you have that black plastic retainer in place, you should consider remove that. There is a high chance that plastic retainer avoid the heatsink to have proper contact to the CPU die.
 
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h9826790

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Apr 3, 2014
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Hong Kong
e.g. This is what I got when I ran the stress test to check the cooling.
Prime95.png

As you can see, there are only 12°C temperature difference between the CPU diode and the heatsink.

In general, when the CPU is under full stress (for more than 3 minutes), that temperature difference should be below 20°C.
 

KeesMacPro

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Nov 7, 2019
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The graphite pad should be the “easiest the apply”, and “hardest to go wrong” solution. And it has very high performance, basically same as the high end silicon base thermal paste.

My Radeon VII shipped with graphite pad rather than the normal thermal paste from factory. Even I replace that by liquid metal, the temperature improvement is just about 3°C (usually I can get 10-15°C improvement from thermal paste to liquid metal).

I personally very OK to use liquid metal, and know how to prevent accident. But if not, my second choice will be graphite pad now. Especially I know that's re-usable. And it won't "dry up".
Thx for the info, never too old to learn :)
I might go for this pad for the next GPU repaste .

If I remember well, a few years ago I tested this pad on a NorthBridge of a cMP , it worked fine and no real difference compared to thermal grease.
 
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Macschrauber

macrumors 68030
Dec 27, 2015
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@Jackdown_101

2nd that, delta heatsink-cpu die is much too high.

Guess there is a gap between the cpus and the heatsink.

I bet on the black seal is too thick If the spacers are used. I prefer cutting down the seal and use the spacers.

or there is too much tin on the die. It has to be polished until the copperish surface is shown. It has to be perfectly even.

the delidded cpus should look as closely to the original cpus as possible. So you can screw the heatsinks down with the correct torque.
 

Jackdown_101

macrumors member
Original poster
Feb 28, 2017
40
5
That 99 is not a problem. You can ignore that number. It means nothing on the cMP.

HOWEVER, your CPU's cooling is very very bad. Only very little heat can transfer to the heatsink.

You should NOT stress the CPU anymore until you fix the thermal paste / heatsink contact.

If you have that black plastic retainer in place, you should consider remove that. There is a high chance that plastic retainer avoid the heatsink to have proper contact to the CPU die.
That's what I was afraid someone would say.

Thanks guess I'll be breaking the allen key and thermal paste out again ASAP.
 

KeesMacPro

macrumors 65816
Nov 7, 2019
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@Jackdown_101 :

In case you're going to remove the black sealer : take care not to damage the capacitors (tiny silver blocks) on the surface with the knife .
For polishing the heatsink contact surface: a save way is to put some paper tape (painters tape) on the CPU over the surface around the copper part to avoid particles getting on the contacts (and remove the tape after polishing it).
A common way to polish it perfectly flat is to tape a piece of polishing paper ( gradually going up from e.g. nr 1000- 2500) on a glass plate (on the table) and hold the CPU upside down to polish the top.
Once done, clean it thoroughly with isopropyl or if not at hand with 97% alcohol.
 

Jackdown_101

macrumors member
Original poster
Feb 28, 2017
40
5
Thanks for all the responses people.

There was indeed some sealer left on the CPU's etc. I was also concerned if the new thermal pad I'd replaced on the heatsink was slightly too thick...
. IMG_3510.jpg

For now decided against doing too much work. Re-Cleaned, re-pasted and re-tightened the heatsinks.

Screenshot 2021-02-03 at 13.22.04.png IMG_3512.jpg


I was slightly less cautious about tightening everything this time too.

Now have much improved thermal performance (CPU's 30 about degrees cooler at the same stage of the render) but I'll do some more stress testing and continue to monitor everything as I go esp those heatsink temps.

Screenshot 2021-02-03 at 13.01.53.png
 
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