It should be stated from the outset that my chip seems to run very hot, even relative to other e8400's, and my conclusions may not generalize. In my quest to bring temps down I have removed the IHS (no help) and installed fairly high end water cooling (some relief). However, you will likely agree the temperatures that follow are still quite high. I could not rationalize how my system could possibly find stability given these temps - reason told me that I should crash as Core Temp exceeded 95C.
Earlier today I was messing around in Everest and found that one can set it to log readings in Preferences and store this info in a .csv file. Messing around, I ran Prime off and on a couple times so I would have idle and load data. This generated something like 1281 data points. I opened the file in Excel and started playing.
It is interesting to note in looking at the second load phase that you can almost see the transitions from 1024k to 8k to 10k etc. These CPU temps are the ones I have been relying on given the numerous complaints about Core Temp values and my own experience. This got me thinking... I have tons of data I could use to explore this anomaly.
The first thing I noticed was the marked difference in the (ahem) differences of the two measures at idle versus under load. Clearly there is a more pronounced difference between the idle temp readings. This did not strike me as something that makes sense - if both CPU and Core Temp purport to measure the same value (ie heat emanating from the CPU), I would expect the two to be aligned across the entire range of values.
I started manipulating columns and came up with the results above. The difference between CPU Temp and Core Temp at Idle is over twice that under load. Note the standard deviations - the idle values are much more consistent than the load values. So we see two things going on: at idle, Core Temp is much greater than CPU Temp, but consistently so; and at load, Core Temp is only marginally greater than CPU Temp, but has a much greater relative fluctuation.
I began to strongly suspect that Core Temp is not related to CPU Temp in any way nearly as meaningful as we would naively believe it to be. This led me to consider the correlation between the two sets of values.
I found this information to be fairly damning. The correlation coefficients tell the tale - r^2 values of .4744 and .657 respectively indicate only a very weak correlation between CPU Temp and Core Temp. If these were both measures of heat emanating from the CPU, I would strongly expect the correlations to be well above .9. The fact that they are not suggests to me that one of these two measures do not mean what we think they do. I am inclined to believe that CPU Temp is our good old fashioned, well, CPU Temp, whereas Core Temp is a measure of something only peripherally related to CPU temperatures.
So that's that. I attached the raw data in case you'd like to confirm any of my calculations, and I encourage you to use Everest to generate your own. I would love to know if other e8400 users find similar discrepencies, and would also be very interested in seeing if 65nm chips behave in the same manner.
[Note: I had to change the extension to .txt to upload it; rename it .csv or .xls to use it in a spreadsheet. Also, the first graph should read 5 second intervals.]
Reply With Quote
Bookmarks