TAT vs. speedfan inconsistencies between cores

[graysky]

If I run both TAT and speedfan, the Intelcore temps are different. Yeah, yeah, I know, I read the thread that explains they should be 15 °C off. On my system, I can calculate an average difference which differs for each core. Not only that, but the difference changes if the machine is in an idle state vs. a load state.

What I did was simply run 2x orthos, then log the temps in both speedfan and TAT (you can write a log in TAT after the time period is up). After I parsed out the non-temp data from the logs, I simply averaged the numbers per core. If I subtract the TAT temps from the speedfan temps, I get the average differences, which as I said are both different per core, and different for an idle vs. load state.

For my setup (P5B-Del and Q6600 @ 9x333) I get the following:



Anyone else willing to try this experiment? If you don't want to or know how to do the averaging in a spreadsheet, you can email your logs to me and I'll do it for you.

[aidanjt]

I've noticed the same 'anomolies', it's the way the CPU reports it's temperature, which requires applications to interpret the negative value correctly, if the calibration is off the results are off. Personally, I'd be inclined to believe that TAT is better calibrated, your motherboard should come with a utility for monitoring, which would also be pretty well tuned.

[graysky]

The asuspcprobe II doesn't actually give core temps (IntelCore sensors), it only gives a single tcase temp via the Winbond W83627DHG. To give you an idea just how far off that sensor is, speedfan is reading the following at idle:

Core 0: 24C
Core 1: 25C
Core 2: 23C
Core 3: 23C

The winbond sensor is reading 18C.

[Mithrandir]

What is TAT? I use speedfan and also Coretemps
Mind you I don't have dual or quad core

[aidanjt]

What is TAT? I use speedfan and also Coretemps
Mind you I don't have dual or quad core

TAT is Intel's Thermal Analysis Tool, it's used to stress test Intel's modern line of dual core CPUs.

[graysky]

I figured out what my problem was. TAT sucks for reading temps on C2D chips. I should have taken a hint from the application itself. If you launch it and look in the upper left under Processor Details, you'll see, "Processor: Pentium M." I just ran RMClock and Speedfan and had both apps log a set of load temps. Then I meticulously analyzed the log files and averaged the exactly (down to the last second) the same time points from each log to ensure a fair comparison. If I take the difference of the average RMClock core temp numbers and the average Speedfan numbers, I arrived at:

Core 0: 15.002
Core 1: 15.069
Core 2: 15.049
Core 3: 14.979

Conclusion: Speedfan can log temps as precisely as RMClock can and the offset is indeed -15 °C. Also, don't use TAT for a C2D or Quad C2D!