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CPU core temp and cpu temp question

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July 24, 2014 10:04:10 PM

Ok, so I've got a few questions and I'm hoping that somebody who really knows can offer some answers about them. I've tried several temp monitoring utilities including core temp, hwmonitor, AMD overdrive and about five others. I've finally settled on HWinfo per a recommendation by SR71 Blackbird and I like it better than the others. The first problem though is that I guess I don't understand the difference between the temp I get for core0 which is showing like 22c and the cpu temp which is showing 39c? Is the cpu temp higher because the sensor is showing an accumulated temp for all cores as compared to just the temp per core sensor? Also, why is it that every one of these temp monitors shows me one temperature but if I close it and reboot to BIOS, which takes all of about three seconds, there is a significant difference between what the hardware monitor in BIOS shows and what these monitors show, for cpu temp. So, when HWinfo (Or any of the others) is showing me 39c and I go immediately to the BIOS (Again, about three to five seconds) the hardware monitor there is showing 46c. How can there be a 7 degree difference that quickly with the fan running full on and which reported temp is more accurate? I know that in the BIOS all cores are under load but it should take some time for that to change that much and if I leave BIOS and go to Windows, with ultra fast boot, and open my monitor immediately, there it is, 39c. All of this is with a stock fan and is loosely related to the thread outlined here: http://www.tomshardware.com/answers/id-2231932/fx8320-i...

I'd really, really appreciate some enlightenment on both these situations if one of you can make sense of them. Thanks in advance for the help.
a b à CPUs
July 24, 2014 10:45:58 PM

darkbreeze,

Temperatures respond directly to changes in load within milliseconds. 3 seconds (3,000,000 milliseconds) is an eternity to a processor. The clock speed of a processor at 2.5 GHz is .0004 milliseconds. By the time you can transition from Windows into BIOS, temperatures have long since changed countless times.

The temperature you see in BIOS is Socket temperature, which is synonymous with CPU temperature, and is calibrated to lookup tables coded into BIOS for each processor variant for your socket type. Code can vary greatly between BIOS vendors and version updates. BIOS or CPU temperature can be wrong by as much as 30C. This issue is not an AMD or Intel problem; it's a BIOS problem common to motherboard manufacturers.

However accurate / inaccurate it may be, the higher CPU temperature in BIOS is the result of boot voltage, which is transparent to core voltage, but is high enough to ensure that the processor will boot under any circumstances. As such, the CPU temperature in BIOS is correspondingly higher than the CPU (Socket) temperature in Windows at idle.

Core temperatures are factory calibrated by the manufacturer (AMD, Intel). Since the heat sources originate within the cores, their temperatures are higher than CPU (Socket) temperature. CPU temperature is the overall temperature of the entire processor, which must always be higher than ambient temperature at dead idle.

If CPU temperature in Windows happens to be higher than Core temperature or lower than ambient, then it's simply wrong due to poorly coded lookup tables in BIOS.

Also, have you read this Sticky? An Understanding of Temperature on AMD CPUs and APUs - http://www.tomshardware.com/faq/id-2122665/understandin...

Or this one? Intel Temperature Guide - http://www.tomshardware.com/forum/id-1800828/intel-temp...

Although the terminology differs somewhat, the principals are the same.

I hope this explanation answers your questions. Now relax, have a beer and enjoy your rig!

CT :sol: 
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a b à CPUs
July 25, 2014 12:18:54 AM

Thanks for that info Comp, it does all make sense, and I did read those stickies prior to looking at different monitors but it didn't answer the questions I had. So are you saying that the BIOS tables in my ASRock board are poorly coded in general, for this model of board, for everybody with the same BIOS version, or is it something that's hard coded into incorporated hardware on the motherboard, or, that it can be different for each individual motherboard regardless that it's the same model and has the same BIOS installed? Also, just wondering (I and know it's almost an impossibility but I have to ask) if there is any possibility that different cooling fans affect reported temperatures, aside from the obvious aspect of their different cooling capacities? I just don't get why my temps were so high with the coolermaster 212 EVO and are evidently in the normal range with the stock cooler. I tried several different configurations and thermal pastes with the 212 and nomatter what it heated up extremely rapidly as soon as I powered up. I mean literally like a degree per second. Swapped it out and normal operation. The only difference I can see is that it operated at like 1400 RPM compared to the stock cooler at about 4500 RPM. Of course it was a 120mm fan and the stock one is only like a 60 or 80. As I mentioned in my other thread, I did however turn off the automatic Turbo core feature though but I don't know how likely that was to have been affecting temperatures while in the BIOS. Seems like it wouldn't really kick in until booted into windows. Shouldn't the CPU have been cooler with the 212 installed as compared to any operating environment with the stock cooler, despite the fact that ASRock indicates a top down cooler should be used, which I assume is due to the VRM's needing the airflow.
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a b à CPUs
July 25, 2014 12:51:38 AM

(1) Adjust your thinking to the fact that temperatures respond to changes in load instantly.

(2) Applicable BIOS tables are motherboard model / BIOS version / processor variant dependent.

(3) Yes, of course, different coolers directly affect reported temperatures, most at 100% workload and least at idle.

(4) I can't address the issue with your 212 EVO, except to suggest that perhaps there was an unseen problem with the mounting bracket, which may have interfered with the heat sinc seating properly.

(5) In a properly ventilated case, the VRM's get sufficient cooling, so there's no problem with using aftermarket linear flow air cooling, or liquid cooling.

Also, just a friendly suggestion; your posts would be much easier to read and decipher, if you broke your single long paragraph into several smaller paragraphs of individual questions, ideas, or thoughts.

CT :sol: 
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