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Which core temp monitor to use for E8400 E0?

Discussion in 'Overclocking & Cooling' started by Pum, Nov 7, 2008.

  1. Pum New Member

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    Hello TechPowerUp people of wisdom:respect:

    I just built a system with an E8400 E0 CPU :toast:

    I downloaded HWmonitor.exe to monitor CPU temperatures, as I like it's appearance best. However, I noticed it reports a single value for CPU temp from the chipset, which corresponds to the "CPU temp" reported by the monitor in EZ-Tune that came with my Gigabyte mobo, and it also reports seperate, higher values for CPU core temps :wtf: This puzzled me, so I ran Core Temp too, and that reported lower core temps :confused:

    So I googled and found several explanations about this sort of thing, best of which seems to be this article:respect: http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=3251&p=4

    What it seems to be saying is that you can't necessarily rely on core temp reading from any monitoring util, but some may be better than others depending on how well they've judged/guessed the Tjunction reference value for the particular chip and stepping - eg: one util may be better for E8400 C0, but another may be more accurate for E8400 E0.

    Now, when I get my system bedded in and start trying to OC it, the perceived wisdom seems to be that I should aim to keep my core temps below 60C, but according to what? So, which util should I measure core temps with on this particular CPU and stepping? Which is best? What temps are others running OCed E8400 E0 at, and what are you using to measure those core temp values?

    thanx in advance, Pum :rockout:
     
  2. Mussels

    Mussels Moderprator Staff Member

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    Realtemp.

    Its the only accurate one.
     
  3. 95Viper

    95Viper

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  4. Pum New Member

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    OK, I did some more testing and research on this. First a correction: I remembered wrong when writing the first post - HWmonitor and Core Temp report the same values for CPU core temp. Real Temp reports 5C cooler.

    As I now understand it, the way these utils find the core temp is that they get a reading from sensors in the CPU, which tells them how much the core temp is below a reference value called Tjmax. So they don't measure an absolute core temp, but a relative one. So they might get a value back like 60C, which means the core is 60C cooler than Tjmax. The util just needs to subtract the value from Tjmax and that's the core temp. So if Tjmax for your particular chip is 100C, then its core temp in this example is 40C. However, if Tjmax were 90C then core temp would be 30C.

    It seems the problem is that Intel do not give a definate reference value for Tjmax for E8*00 CPUs (and some others too.) Intel say that Tjmax can vary a bit between models, steppings and even individual chips. It seems that TJmax for these chips is around about 100C, but each monitor app has to make an educated guess of what value to use. HWmonitor and Core Temp use 100C for Tjmax; Real Temp uses 95C, and so reads 5C cooler at all times. You can change the Tjmax setting in Real Temp if you want. Which is right? Who knows!? I suppose using 100C is the safer option. Anyway, from my testing they are all equally accurate - it's just a question of what value you want to use for Tjmax and which interface and feature set you like best.
     
  5. Mussels

    Mussels Moderprator Staff Member

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    realtemp is teh correct one, because the developer actually tested it himself. The tuning feature is included in realtemp, so that end users can tweak it in if they get new chips, before realtemp is updated to support them.
     
  6. Pum New Member

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    On a related note, for now I'm running my E8400 on stock settings in the GA-P35-S3G mobo BIOS. Using 100C Tjmax reports core temps at idle of 39C/39C, which seems a little high, but would be 34C/34C if I used Real Temp with its default Tjmax of 95C.

    However, when I run Prime95 to load both cores to 100%, the core temps level off at 43C/39C. This seems quite low. I'm running at stock 9x333MHz, vcore set to Auto, etc. The fan on the CNPS 9700 is turn down to minimum. System seems to run perfectly in all ways.

    I seem to remember reading somewhere about "sticky" temperature sensors, and the core temp sensors being more inaccurate the cooler they are (ie: they get more precise the closer they get to Tjmax). Anyone seen similar or got any advice? I'm not too worried about it for now. If/when I OC I expect to push the cores to higher temps, and maybe that will "unstick" the sensors, but I'm not sure it's that simple or likely.
     
  7. Mussels

    Mussels Moderprator Staff Member

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    let me put it to you another way: these are the cold running 45nm chips, you're at stock clocks on high end aftermarket cooling, and you have trouble believing you have a 40C load? think it over again ;)
     
  8. Paulieg

    Paulieg The Mad Moderator Staff Member

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    The idle temps seem slightly high, but your case airflow could be the cause of that. Your load temps seem correct, since that chip had a low VID and it's running at stock.
     
  9. rampage

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    i will bet my car, pc, and rifels and my brothers life that you ahve the same issue as almost every other person with a E8** cpu, the temp sensors are stuck, you will not have a accurate idle temp but your laod temps will be correct, my e8600 @ 3.33 ghz @ 1.0v and a water cooling it is saying its idleing at 34/39c but if i OC to 4.7ghz the cpu its still ideling at 34/39c but at load it jumpes up to 48c or so

    as far as i know you cant unstick stuck sensors, its just the one fault with the 45nm chips

    realtemp is the best software for readingt he temps so far and you load temps seam just fine, if you want lower load temps at stock speeds try undervolting the cpu, it should work down to the 1.1 / 1.0v mark at stock
     
  10. Mussels

    Mussels Moderprator Staff Member

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    oi biatch, my life is not for you to bet.

    He probably is correct tho, that your idles simply cant go below a certain reading.
     
  11. Pum New Member

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    Seem a little uncertain there - are you sure? :rolleyes: :D

    Yeah, 'tis what I figured - cheers :toast: Partly I wanted to get this down somewhere that people googling on this kind of thing could find and hopefully get a quick simple answer. Took me a little while of searching and thinking to get to the bottom of it.
     
  12. dark2099

    dark2099

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    From what I have noticed from most of my E0 stepping chips, they tend to idle a little higher, but the load temps are generally around avg to a bit lower than avg.
     
  13. Konceptz

    Konceptz

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    The newest HWmonitor gives me numbers lower then real temp, so i'm sticking with HWmonitor, plus the make a 64bit version for us 64bit guys and features ESA support.
     

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