There is a temperature sensor bug affecting the whole Core 2 line, some sensors dosnt show correct temps under ~40C. When it comes to load temps over ~50C the sensors shoud always be "correct enough".

Skyscraper wrote:

There is a temperature sensor bug affecting the whole Core 2 line, some sensors dosnt show correct temps under ~40C. When it comes to load temps over ~50C the sensors shoud always be "correct enough".

Do a run of Prime95 for a while to test your setup. That'll show any actual issues.

Under load the two hotter cores stay about the same while the cooler ones heat up to about same as the other 2.
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At stock settings a Q9550 dosnt get hot at all with a good tower cooler, ~30C idle ~45C load is normal.

The difference is normal while for some the temps are closer together if the IHS is nice and flat, Core 2 Quads are just a pair of dual cores on the same substraight (MCM). You could look into lapping to even the temps a bit.

nforce4max wrote:

The difference is normal while for some the temps are closer together if the IHS is nice and flat, Core 2 Quads are just a pair of dual cores on the same substraight (MCM). You could look into lapping to even the temps a bit.

The very uneven idle temp is a super common known bug often called "stuck temp sensors", uneven load temp however is often caused by the reasons you mention.

With stock cooling you rarly notice this bug as most stuck temp sensors come alive at ~40C. The bug is most easy to notice with a well cooled 2+2 core quad like Nahkris.

Yes, one of the sensors on my QX9650 is stuck at 35C (according to RealTemp), but as you say, it starts working normally when the temperature rises above that point.

Strangely, RealTemp claims that the other three cores are currently at 19C. This doesn't make any sense to me, since the ambient temperature is higher. Everest reports temperatures 5C lower, and CoreTemp 5C higher. I wonder what causes the same sensors to be read so differently by different utilities.

dr_st wrote:

Yes, one of the sensors on my QX9650 is stuck at 35C (according to RealTemp), but as you say, it starts working normally when the temperature rises above that point.

Strangely, RealTemp claims that the other three cores are currently at 19C. This doesn't make any sense to me, since the ambient temperature is higher. Everest reports temperatures 5C lower, and CoreTemp 5C higher. I wonder what causes the same sensors to be read so differently by different utilities.

They sensors read the temperature as degrees from maximum CPU temperature and then the program translates the numbers to actual temperatures. If the program do not know the correct maximum temperature for the CPU then it will show the wrong actual temperatures.

The cores are arranged on 2 dies (2 cores per die) on some CPUs. Maybe the HSF pressure is uneven?

FYI the Q9550 comes in two flavors: C1 and E0 stepping. The C1 tends to run hot and the E0 (your chip) is the good one which runs cool. I used this processor several years ago and loved it.

Snayperskaya's suggestion that the heatsink is making an odd contact with the heat spreader would be my guess. But this chip is pretty safe up to 70C if I remember correctly.

I overclocked the cpu to 3,4 and now all the cores idle around 38-39 C so no more 10 degree difference.
In full load they go up to around 56-58.