e8400 Core Temp: Data Analysis Confirms it is Largely Meaningless

[cadaveca]

Yes, Core temp and cpu temp are not the same...they never have been. While your results are interesting, I find it hard to take for full value; the thread title lead me to beleive you had REAL data, not just data from one cpu. one cpu does not create fact, except for that particular cpu.

E8400 and temp reporting accuracy varies from cpu to cpu. Why, I don't know, and like you, I really could care less about temps.


But I will tell you this, temps may not affect cpu stability so much, at higher levels, but THEY WILL MAKE THE CPU'S LIFE MUCH SHORTER. "They" being high temps, of course.


So, get about 100 or more cpu's run the same tests, correlate, then your thread title would be accurate.

Maybe look into WHERE on the cpu the CORETEMP sensors are...you may just find that this is the HOTTEST part of the cpu, while cpu temps are related to overall temp of the silicon die/dies.

remember, that cpu temp is a single value for quads...but there are two wholey seperate pieces of silicon. So, for quads, cpu temp reports what? Again, overall temp, not the hottest part of each die.

[jonny_ftm]

I second cadaveca too.
Your results are not that abnormal. CPU temperature is anlog reading somewhere on the die, between the cores. Removing your IHS also suerely makes your CPU readings no more reproductible with other CPUs.

It is just normal, that the more you increase the load/heat on cores, th emore they get hot while CPU temperature will increase in a slower manner. This is just normal physics, as the source of the heat is the cores where DTS sensors are, while CPU temperature is far away from the cores.

Personally, I'm not shocked by your results. Even without removing the IHS, the linear relation between coretemp (deep temp) and IHS temp (superficial temp) is lost on high OC.

But, other reports on DTS sensors being freezed is more than abnormal.

What you could do is use a temp sensor and put it on one core, and another on the CPU die. You'll see that they confirm the non linear relation

[ixtapalapaquetl]

@cadaveca, johnny_ftm

First and last sentences from first post:

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.

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.

I do not disagree with either of you. But if the above statements were unclear, allow me to try once again: I am simply requesting that others who are interested in the odd behavior in 8400 temperatures perform a similar analysis so that we might see if this phenomenon extends beyond one CPU (as I suspect it might).

Procedure:

1) In Everest, File->Preferences->Logging
2) Check "Log sensor readings to CSV log file:" and choose destination directory.
3) Check Time, CPU utilization, CPU Temp, and Core #1/Core #2 Temp.
4) Run at idle and under load long enough to generate significant data. It may be easiest to Prime overnight (at high overclock) - set it and forget it.

5) Open .csv log with Excel.
6) Sort by CPU utilization column.
7) Create a new column: Core Temp entry - CPU Temp entry.
8) Using this new column, find averages, standard deviations of 100% usage and non-100% usage for CPU Temp and Core Temp. Post results.

9) Create a scatter plot of CPU Temp vs. Core Temp for 100% usage. Include trendlines, correlation. Repeat for non-100% usage. Post results.

As you pointed out, this might very well be an isolated case. And it might not. I strongly suspect that we will not see the same behavior in 65nm CPU's as we do from these 8400's. Unfortunately I have but one CPU, and thus cannot investigate further without assistance. If my suspicion bears true, we will possess solid information to begin theorizing on causes. If not, we are merely left in exactly the same position we are now - namely, speculating without data.

[jonny_ftm]

I could try it, I'll see...

But, I still can't understand your questionning. It is well established, since the Core2 begining (quiet 2 years now) that there's no good correlation between CPU temp and Core temp. So, it is normal you won't find any correlation in your analysis. The reasons are many, like I explained above (sensor technology, position, Internal Heatsink...)

Also, all trials to understand how those coretemp sensors work ended to a fail. In fact, Intel never published the full spec datasheets on those DTS sensors. All programs run on a guess and try based on many CPU samples and comparisions between ambiant and coretemp on idle, low volt and under clocked CPUs.
The thermal throttle point was prooved to be more correlated to core temp than CPU temp.

So, yes, don't expect to find a correlation between those values, that's really well known. That's all I'm trying to explain.

Now, the 45nm DTS sensors being different than on 65nm, is something I never read about. It is too early to state it as most 45nm CPUs, especially quadcores aren't out yet.

I will see if I can do the stats you ask for, as, in any case, I don't expect to see any correlation