6 Replies Latest reply on Jul 31, 2011 6:28 PM by robp

    i7 870 CPU temp higher than core temp

    robp

      I recently built a system with an i7 870 CPU and an Asus P7P55D-E LX motherboard - I've also added a Zalman CNPS9500 cooler. I'm wanting to make sure my temperatures are ok (I do a lot of video encoding, which means running high loads for long periods while unattended).

       

      I've downloaded several utilities for monitoring temperature (speedfan and ReakTemp, as well Asus' PCProbe). What's concerning me is the difference between what these programs are reporting for my core temperatures compared to the CPU (I assume that is the T-CASE?) temperature. All the research I have seen suggests that core temps should be higher than the CPU temp, but I'm seeing the exact opposite. My CPU temps seem to average about 8 degrees higher than the cores.

       

      At the moment, I have Hyperthreading turned off in my Bios, because the CPU temps start to get over 80 degrees under stress testing with Hyperthreading enabled. However, if I trust the core temperatures, then that would put it at about 72 degrees.

       

      My question is, what could cause such a difference between the core and CPU temperatures? All 4 core temps are consistent to one another (within 1-2 degrees), so I assume they are accurate. Could it just be a faulty T-CASE reading? Should I even be concerned?

        • 1. Re: i7 870 CPU temp higher than core temp
          robp

          FWIW: I recently tried with another processor, and there was the same difference between the core temp and the "CPU" temp - so, I guess it's not a problem with the processor.

           

          But, I still don't know if it's normal for the CPU temp to be higher than the core temps. Could this be a motherboard problem, is this normal, and which temperature should I pay attention to? Right now, I'm afraid to let it run very hard for long periods, especially when I can't be there to constantly monitor the temperature.

          • 2. Re: i7 870 CPU temp higher than core temp
            mechbob

            This could be a temp sensor on the board it self , Do you have the potion to RMA the board.

            • 3. Re: i7 870 CPU temp higher than core temp
              robp

              Well, not through the retailer I purchased the motherboard through. I guess I could try to RMA it with Asus.

               

              Is there any other way to verify a problem with the motherboard? I'd hate to ask Asus to replace it if nothing were wrong.

              • 4. Re: i7 870 CPU temp higher than core temp
                mechbob

                If ASUS does dot find anything , the most it will cost you is freight. Been there done this .

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                • 5. Re: i7 870 CPU temp higher than core temp
                  parsec

                  In my experience, you are correct that usually core temps are (or are displayed) higher than an overall CPU temp, on socket 775, and 1366 CPUs (which may be an overgeneralization.)  My i7-2600k (socket 1155) does not do this, the core temps are always lower or equal to the CPU temp, and the maximum CPU temp is equal to the max core temp.  AMD CPUs may be different in this regard.

                   

                  Either way, the CPU's thermal management, as in protecting itself from thermal damage, is not dependent upon a single core temperature, as far as I can tell reading Intel's technical documents.  There is only one Digital Thermal Sensor (DTS) which triggers the thermal protection function, and "core temperature(s)" are never mentioned in the document whatsoever.  The hardware monitoring program provided with earlier Intel mother boards did not display any CPU temperature, only the remaining interval until the CPU was over heating.  I think current versions do, but likely only because users want that.  In reality, a simple temperature alone does not indicate if a CPU is overheating.  For example, a CPU would be over heating if it is at 50 degrees C, but only dissipating a fraction of it's rated TDP.

                   

                  Frankly, I can't find where the data for a core temperature even comes from, in the Intel documents.  All temperatures related to a CPU are calculated using two or three factors to derive a temperature, they are not direct thermometer readings.  In order to determine why there is a difference between "core temperatures" and CPU temperatures, we would need to understand how they are determined in the first place, which I have never seen explained anywhere.  We all like to think of things in simple terms, but at times things are not that simple.

                   

                  Unless other i7-870 CPUs display there temperatures in different ways than yours, I doubt you have anything to worry about.  I don't have experience with socket 1156 CPUs myself.

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                  • 6. Re: i7 870 CPU temp higher than core temp
                    robp

                    Thanks for all the information and advice. Still not sure what I'm going to do, but you've all been helpful.