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Which one of the CPU Temperature is correct?

Last response: in CPUs
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July 15, 2012 4:46:17 AM

Hello,

I built my new system myself. It has ASRock Z77 Extreme 4 and I5 3450 processor and uses Cooler Master Hyper Evo 212. When I boot my CPU and go into BIOS, it shows my CPU's temperature as 40 degree.

But when I installed RealTemp: http://www.techpowerup.com/realtemp/

it shows as 33, 33, 36, 35 (for 4 cores)

My question is which one should I believe? Should I believe motherboard's CPU temperature or this tool?
a c 185 à CPUs
July 15, 2012 4:55:37 AM

In BIOS your processor is under a little load. This is because C1E which idles your processor and lowers your voltage doesn't kick in until you boot into an OS.


That's why you have slightly higher temperatures in BIOS than in Windows.
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a b à CPUs
July 15, 2012 4:55:42 AM

What is the ambient room temp?

Those would be expected idle core temps. The BIOS temp is NOT a core temp, but the temp inside the heatspreader called Tcase. It seems a bit high but I would say with no further data it is wrong.
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July 15, 2012 5:00:33 AM

@amuffin: Thanks.

@Proximon: The room temperature is around 32-34 degree Celsius
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a b à CPUs
July 15, 2012 6:14:28 AM

So the room temp is 90 degrees Fahrenheit? Really? Then the core temps are obviously wrong.
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a c 185 à CPUs
July 15, 2012 6:36:05 AM

Proximon said:
So the room temp is 90 degrees Fahrenheit? Really? Then the core temps are obviously wrong.

Those temperatures are not possible, you can't idle at ambient temperature with a heatsink.
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a c 188 à CPUs
July 15, 2012 6:47:38 AM

try open hardware monitor...the temp you want to look at is the cpu case temp. it should match close to the same temp as the bios is reading.
http://smg.photobucket.com/albums/v340/plushdragon/?act...
asus mb with a 3540...as you can see soem of the temps show real low..those ones not running and good case airflow.
the temp that inportant on the ib and sb is cpu case temp sensor. that the temp reading for the whole cpu.
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a c 116 à CPUs
July 15, 2012 7:18:45 AM

amuffin said:
Those temperatures are not possible, you can't idle at ambient temperature with a heatsink.

Thermal diodes in CPUs are non-linear and their associated support circuitry is not calibrated. They can be off a handful of degrees either way around the real temperature within the silicon due to process variations between batches and even between different locations across the wafer.

Depending on luck, it is quite possible for people to get CPUs that cannot be cooled below "30C" under normal circumstances without using some form of heat-pump or cryo-cooling.
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a c 185 à CPUs
July 15, 2012 7:20:35 AM

He could have gotten a lucky chip?

But, THAT'S HOT! :ouch: 
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a c 116 à CPUs
July 15, 2012 8:04:43 AM

amuffin said:
He could have gotten a lucky chip?

The point was that the core temperatures are only a relative indication of temperature good enough for internal functions such as thermal throttling, not an absolute temperature measurement. The error on it is likely something in the neighborhood of +/-5C so you can have a chip running at 30C actual core temperature reporting as 35C or vice-versa.

The CMOS process used in CPUs is tuned for low-power high-speed CMOS gates, not precision PN junctions and precision ADCs needed to sample the diodes' output.
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July 15, 2012 8:07:27 AM

smorizio said:
try open hardware monitor...the temp you want to look at is the cpu case temp. it should match close to the same temp as the bios is reading.
http://smg.photobucket.com/albums/v340/plushdragon/?act...
asus mb with a 3540...as you can see soem of the temps show real low..those ones not running and good case airflow.
the temp that inportant on the ib and sb is cpu case temp sensor. that the temp reading for the whole cpu.



This is my hardware monitor:


upload pictures

Does anything look suspicious to you? This PC is assembled by me and this is the 1st time I've done it. Hope I've not done it wrong :) 
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a c 188 à CPUs
July 15, 2012 11:43:39 AM

your temps and everything look fine. my temps are lower as my cpu fan blows down on the mb and not across like the 212.
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July 16, 2012 12:26:37 PM

Best answer selected by salman4u.
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