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AMD Temp Information and Guide - Page 6

post #51 of 117
Quote:
Originally Posted by symmetrical View Post

Hello all, new here to overclock.net but was mostly browsing as a guest. Anyway I wanted to share some interesting information. I basically had a quest to find out what is going on with the CPU temp vs Core temp theories. So I e-mailed AMD, got their response and quite frankly I was not satisfied. Here is the response:

"Thank you for contacting AMD. The maximum temperature listed for our processors refers to the overall CPU Temp. So, the best application to monitor your processor temperature is from your motherboard manufacture. Dependant on your motherboard manufacture, the manufacture company will have a processor monitor application that you can dowload and use to monitor the temperature of your CPU. Lastly, the best processor temperature reading is Core Temp.
In order to update this service request, please respond, leaving the service request reference intact.
Best regards,
Francine
AMD Global Customer Care"

Now that didn't really answer my question which originally was "Which temperature is important to monitor, CPU temp or Core temp?"

Now based on ALUCARDVPR's previous information, AMD suggests Core Temp is what we should monitor.

On my FX-8120 I was getting 54C on CPU temp and 33C on Core Temps on STOCK SETTINGS NO OC. I have a Corsair H80 cooler. This made no sense to me that with this cooler I was getting up to 54C on load. Ambient temperature is 20C in my room as well. So this made me realize that Core Temps is probably more accurate.

But to further strengthen the argument that CPU temp is actually just a Socket Temp BELOW the socket, I opened up my case and put a nice cold fan right behind the Mobo. Low and behold, Core Temps at load remained the same while Socket temp reduce by about 7C.

So this brings me to the conclusion that it probably is more accurate to monitor Core Temp seeing as how the top of the CPU is what's actually attached to the cooler while below the socket will theoretically run hotter.

Yeah these temps make sense. I have an FX-8120 with an H60 and my core temp reaches around 38c under load (no OC) while my CPU temp also sits at 54c.

5c difference between the H60 and H80 sounds dead on.
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post #52 of 117
hey i am getting confused what temp shound i trust in asus software or aida64 or hw monitor the cpu temp are core temp on my 955be... thanks for help.
post #53 of 117
Quote:
Originally Posted by skyline_king88 View Post

hey i am getting confused what temp shound i trust in asus software or aida64 or hw monitor the cpu temp are core temp on my 955be... thanks for help.

Core temps.
post #54 of 117
NOWWWWWWWWWWWWWWWW I got it.

Been reading the wrong temp all this time. all though my local ambient temp is usually in the 80's (F) I now breathe a bit easier. I am now sitting around 52-53C while stressing under IBT (known to produce more heat than Prime95 for example). All this at 4Ghz, 1.35V and a H100 with P/P configuration.

85
post #55 of 117
For additional clarification, here is an practical example from an AMD Bulldozer 6-core CPU. In this example core temperature in idle mode is about 10C (not accurate at all), ambient air temperature was about 25C at this time. Analog CPU temperature sensor in socket delivers 30C, which should be close to reality.

Then, 3 out of 6 cores were put under load, the core temperature value approaches the CPU temperature fast and seems to be accurate then. This coincides with various statements found here and elsewhere, that AMD core temperature is designed to accurately read load temperatures, but not idle temperatures.

After discontinuation of CPU work load, previous difference between core and CPU temperature can be seen again. Of course, analog CPU temperature sensor in this example seems to perform pretty well (Asrock 970 Extreme4), which may not always be the case on other mainboards.

334
post #56 of 117
THANK YOU!! smile.gif You have answered what many have not! lol:thumb:
post #57 of 117
Gosh dang to heck! I have been reading core temps all this time and some dude tried to tell me that my system was unstable due to temps and that I should be reading the other numbers. Now I have been reading the wrong temps since then. GRR!
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post #58 of 117
post #59 of 117
Quote:
Originally Posted by dazz. View Post

I don't get it.
In the AMD Thermal Design Data Sheet the Tcase max is greater lower than the TCTL max
http://support.amd.com/us/Processor_TechDocs/43375.pdf
Maybe Tcase is not really that "CPU temp" sensor reading in the socket then?
From 41256:
So if Tcase is meassured at the máximum cooling point, it must be lower than the core temps.
Anyway, not going to argue that if AMD says it's Core Temp, it must be Core temp. Just curious

Tctl = Not an actual reading but a point of reference. AMD's cliff notes explanatiion -

"As for Tctl, there is a technical definition at http://support.amd.com/us/Processor_TechDocs/41256.pdf on page 73 that (tries to) explain it. As a very crude Cole's Notes version, it doesn't measure temperature as much as it is a sliding scale that refers to the processor's current temperature as it relates to the temperature at which the cooling fan has to get to 100% to hit the maximum case temperature (TCaseMax)." (hence the use of "control" ctl in the name)

Tcore = Again not an actual physical reading but a reading derived by taking the closest thermistors (Tcase thermistors) on the die package (not on the die itself but in the package itself that the die sits on) and using a formula to derive the approximate "core" temp. It's for that reason it's not used as a "maximum operating temp".

Tjunction = The thermistor on the motherboard underneath the socket where the pins from the CPU make contact (hence the name "junction"). Also not an accurate way of measuring the temperature of the CPU which is why they stopped using it as a basis of that with the K7 CPU's (Athlon).

Tcase = A "CPU Temp" output from the CPU itself. This started with the K8 architecture. It's taken from the thermistors on the die package. As AMD explains "There are always more than 1 (at least 2, up to 6-8 potentially, but no elaboration given on how many per model), but the TCase temperature is determined by averaging those values out, done by the processor". It gives an "average" value for the whole CPU die and not just a reading of individual cores. Probably the reason why AMD uses this for the "maximum operating temperature" (Tcase max) as just reading the "cores" ignores other potential hot spots on the CPU (the CPU/NB, IGP etc). (hence the use of the "case" in the name).
Edited by Bubba Hotepp - 6/27/12 at 6:39pm
post #60 of 117
thumbs up bubba,
the stock air cooler take your cpu to 4ghz under turbo and it hit 61c cpu temp,dose that also mean what your saying there?
i mean why would they give you a cooler to keep the cpu temp under 61c?
Edited by MrPerforations - 6/27/12 at 7:00pm
    
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AMD™ Ryzen™ 1700 3.75ghz Cool Laboratory™ Liquid Copper MSI™ X370 Gaming Pro Carbon™ Gigabyte™ Radeon™ R9 280 950/1070 Crossfire 
GraphicsRAMRAMHard Drive
Gigabyte™ Radeon™ R9 280 950/1070 Crossfire Avexir™ Blitz™ 3200 CL16 @ 3200 Crucial Ballistix™ Active Cooling fan Seagate™ 2TB Barracuda™ 
Optical DriveCoolingCoolingOS
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