Phenom II 550 X2 reads higher temps for CPU(case) than core?

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CoreTemp-User301
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Phenom II 550 X2 reads higher temps for CPU(case) than core?

Post by CoreTemp-User301 »

I have the Gigabyte GA-MA790X-UD4P motherboard. Until today, it ran an Athlon X2-6400+ mildly OC to 3.3 ghz (100 mhz over stock) with the stock HSF (the bigger one with the copper base and the heat pipes). It idled (cpu case) according to EasyTune 6 (the Gigabyte utility) at around 37 and got up to about 60 when running Prime95. This was certainly within expectation. Both cores under CoreTemp 0.99.4 read slightly different numbers, but they were higher than the cpu(case) reading, as expected. (I am operating under the presumption that the reading reported simply as "CPU" by the EasyTune6 program is interchangeable with the cpu(case) temp, even if that is not technically true).

I didn't take much note of the exact readings of the cores when I was running the 6400+, since the AMD max heat spec of 63C refers to the case temp, with no core temp given. They were, to the best of my knowledge, about 10-15 degrees higher than the cpu(case) temps.

Now, I have upgraded to the Phenom II 550 X2. It is OC to 3.6 ghz (500 mhz over stock) and running with the Arctic Cooling 64 pro HSF (about three times bigger than the stocker). With the much bigger HSF and the thermal specification of the chip at 80w vs. 125w for the 6400+, I would expect lower temps even with the bigger overlock.

Now this chip only reports one temp for all the cores, not individual core temps as the 6400+ does. The reading at idle was 32C on the cores (as reported by CoreTemp) and 41 on the cpu(case) (as reported by EasyTune6).

Isn't a case temp higher than core temp actually... impossible?

I started up Prime95 and both the core temp and the case temp increased. The core temp topped at 42C while the cpu(case) temp topped at 54C. The delta is a little larger, with the cpu(case) temp again higher than the core temp!

This same motherboard was able to report what I think are likely to be accurate cpu(case) temps with the other cpu. Now, though, something is fishy with the core temps being lower than the cpu case temps, and I tend to suspect the cpu(case) temp is the screwy one. With the much bigger HSF and the chip with 45w less TDP, I would expect idle temp to be lower than with the 6400, not higher.

Now I know the load temp is really what matters, and that my load temp of 54 is well within the safe range. However, I do have a reason for trying to nail this down beyond curiosity!

This motherboard is one of the ones that is able to unlock the extra 2 cores of the Phenom II dual core. When I do this, the chip effectively becomes a 125w quad core Phenom (and probably a bit more since it is OC). But this bigger HSF should be able to hold the 125w Phenom temps down better than the relatively small stock AMD cooler did with the 125w 6400+.

With the quad cores enabled, unfortunately, I lose the ability to read the core temps! This is an unfortunate side effect of enabling the extra 2 cores... actual as-released Phenom quads don't have this issue.

With mine, Coretemp reports 0C as a quad core. However, EasyTune 6 still reports the cpu(case) temp. However, now it idles at 45C and gets up to 64 while running Prime95.... that's toasty, and is a degree higher than the max temp of the quad core Phenoms (and since that is effectively what I have with the cores unlocked, I think that to be the more pertinent max temp, rather than the 70C listed for the Phenom with 2 locked cores).

I think the rise in the cpu(case) temps when the other 2 cores are enabled is normal. I expect that! But that's too warm for comfort, and the question about whether the cpu(case) temps were accurate in the first place remains.

It's relatively cool in the room where the PC is located right now, but due to circumstances beyond my control, during some parts of the year, the room temperature gets 10-15 degrees F hotter than it is now, and I would like to know that my computer can take it!

What is my cpu temp, really? Anyone?

CoreTemp-User301
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Posts: 2
Joined: Thu Jan 01, 1970 12:00 am

More info

Post by CoreTemp-User301 »

Ok, I obtained a digital multimeter with a temperature probe. On my particular HSF, the copper base plate that contacts the cpu is slightly smaller than the heat spreader built into the cpu case, so it leaves a nice little "step" where I can stick the probe to get a ballpark reading of the case temp of the CPU (on the left side of the cpu as I face the motherboard).

I recorded the following numbers with my Phenom II 550 with all cores unlocked, with my Arctic Cooling Freezer 64 Pro cooler:

At idle:
Cpu(case)(as reported by EasyTune 6): 42
As reported by my multimeter: 33
(CoreTemp does not work with all 4 cores unlocked)

Under full load, Prime95:
Cpu(case)(ET6): 60
Multimeter: 44

Then I removed the Phenom II 550 and put my Athlon X2 6400+ cpu back in. This cpu has a TDP rating of 125w, the same as a quad core Phenom in the 3.0 ghz range (which is what my Phenom effectively is with all cores unlocked).

At idle, I saw these temps with the 6400+:

Cpu(case) as reported by EasyTune 6: 33
CoreTemp: 42,34 on the 2 cores
My multimeter: 33

At max load, prime95:

Cpu(case)(ET6): 49
CoreTemp: 58, 52
Multimeter: 44

I double checked my notes and it's true: both chips recorded the exact same idle and load numbers with my meter. Given the similarity of the CPUs in TDP, and that I was using the same cooler, it's not surprising. What is surprising is the wild differences reported by EasyTune 6 while the Phenom was installed!

The idle temp I noted with my meter on the 6400+ was identical to the EasyTune number, and the load number was fairly close, with a delta of 5 degrees. I would hazard a guess that the EasyTune numbers are right on the money with this CPU.

The results reported by EasyTune 6 with the Phenom are much higher, even though I recorded identical numbers loaded and idle with my meter. The idle temperature was overstated by EasyTune 6 by 9 degrees, and the loaded by 16. Now, if we presume that the 5 degree difference between the multimeter temp and the EasyTune 6 temp would be consistent with that of the Phenom. then the loaded reading in ET6 looks to be overstating the actual cpu(case) temperature by 11 degrees.

It does seem as if EasyTune 6 (which matches the temp reported in the BIOS at bootup and the temp in Speedfan) is reading high by about ten degrees. It may not be exactly accurate to subtract ten degrees from the reported temp, but doing so would (by these numbers) get me within 1 degree of the presumed accurate temperature.

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