Strange CPU Core Temps??

So, the story goes....

I brought my mac pro 3.1 from eBay (2x Quad Core 3.2ghz, 16gb ram, ssd... etc etc)

and i thought let me check the thermal paste after 3 months of ownership... lone behold what i found was what looked like liquid mercury on the cpu and heatsink no thermal paste at all the processor and heatsink were in terrible states.

so i cleaned the cpu's as best i could and took brassco metal polish to make the heatsink remotely what it used to be from the shop.

i also checked north bridge and south bridge and replaced thermal paste on them but they actually had thermal paste and looked in tip top shape unlike the cpu's.

NOW:

when system is idle cpu core 3 (viewed in temperature gauge by tunabelly) = 86C!!!!!!!!!!!!!!! HOWEVER when i perform a stress test in geek bench and currently still am that sum drops to a much more reasonable 59C.

WHY, have these temps dropped in stress tests and rocket when idle?

Thanks in advance if you can help me...

hello bax i have since removed this silver coating and gasket as it was nothing like this and had basically been burnt. so now like most other heatsinks its just bare copper, the temperatures aren't different from before, however, why would the cpu core temps drop when under load but the cpu diode temps rise instead>?

bax2003 said:

The Mac Pro (Early 2008 Dual 3.2 GHz) computer uses a special coating on the processor heatsink and processor to manage the temperature in the computer. The silver-colored coating comes applied to the underside of the heatsink and the top of the processor.

Before installing a new or existing heatsink or processor, always make a visual inspection of the part. Specifically, check the application of the silver-colored coating on the underside of the heatsink and the top of the processor. In addition, check the condition of the gasket that surrounds the coating on the heatsink.

Image

All this info is from Service Manual, specifically for 8-core 3.2 GHz model.

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yes I'm a pc builder and this what i have used and applied with the line method along the cores, same as my pc water block. i just don't get why the temps go up when idol and go down when under stress, you would think it would be the other way :/

carylee2002 said:

I would recommend you get some Arctic Silver 5 and read the instructions from their website. I use Arctic Silver for years and swear by them. You don't gob it on, many times the most you will put on is about the size of a pea or a straight line. I replaced my cpu and my average temps at idle is 38c and in the hot summer months it will go as high as 50c. Keep close attention to prepping the heat sink for the arctic silver to be applied.

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Stress test Below and cooler core temps



and no stress test and hotter core temps below....

h9826790 said:

Please show us how you get that temperature. May be you get the wrong one (e.g. Core temp relative to ProcHot), which is the higher the better.

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Hello yeh i manually override the fans but even if i run them fast with no stress test it still runs just as hot :/

JazzerAlto said:

Looks like it's due to the fan speed being higher under load. I've noticed something similar on my 1,1. I suspect the idle temps are probably fine and it's an attempt to keep the machine quiet.

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here still running fast but still hot when idol :/

so what your seing is ok then? the only reason i ask is that i changed my thermal paste to the arctic silver 5 and wanted to know if these temps were ok?

h9826790 said:

That's the "Core relative to ProcHot" temp, not the core temp. As you can see, the diode temp is actually going up when you stress the CPU, and go down when you manually spin up the fan.

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