i7 950 MAX Overclock on air

[CompuTronix]

unclewebb and rge,

Always a pleasure!

Although I seldom offer comments on the Real Temp thread, I have followed every page, and continue to do so. As such, I am also aware of your excellent work, rge, and I agree with your findings completely.

While I see your point concerning how the paragraph is worded, I believe that Figure 5 "Diode to DTS Temp. difference" refers to the Analog Sensor shown in Figure 1, rather than the Thermocouple / IHS "Tcase" measurements detailed in Intel's Thermal Metrology, which is not discussed in this document. However, considering the lack of a defined scale, it does leave things open to interpretation as to exactly what a "large temperature gradient" means in relative terms.

I realize and appreciate that the scope of your efforts are focused primarily on Core temperatures, however, many enthusiast are continually confused by CPU temperature, and it's significance relatative to Core temperatures, especially when they encouter mis-programmed BIOS, CPU temperatures below ambient or above Core temperature, or a "stuck" DTS. Nonetheless, CPU temperature, when properly calibrated, provides an additional thermal reference which can be quite useful under a number of scenarios.

The following is from post #3531 of 6/16/09 on page 142 of the Real Temp thread:

Hi unclewebb and rge,

Sorry I haven't posted or PM'd for quite some time, however, I've continued to follow your excellent work, as well as every post on every page, every day.

Your points are well taken concerning Intel's deviations in Tjunction Max values, however, from a different perspective, I'd like to share with you my research and empirical data, which I've continued to acquire for my Core i7 and Core 2 Temperature Guide over at Tom's.

During the past 2+ years, I have extensively tested, and recently re-tested and analyzed processor temperatures using three data points which consist of idle, 50% load and 100% load at stock settings with Prime95 Small FFT's. I then repeated each test at overclocked settings with higher Vcore and temperatures. The objective was to observe and carefully document the thermal relationships between CPU temperature and Core temperature, sensor linearity characteristics, slope error behaviors, and power consumption.

Calibrations were based upon the 5c thermal Gradient between the Analog Thermal Diode and the DTS value, of which we're both familiar from certain Intel engineering documents. All testing was conducted using a standardized test setup under controlled conditions at 22c ambient on a variety of motherboards, chipsets and CPU cooler combinations. Real Temp was used to cross-reference Core temperatures in SpeedFan.

Although the CPU temperature offset calibration value may shift on certain motherboard when BIOS test settings are changed, CPU temperature was verified or re-calibrated in SpeedFan prior to acquiring each measurement, so that information from the Analog Thermal Diode would provide a valid and accurate point of reference. This assured that the results were both consistent and repeatable.

The following assortment of 65nm an 45nm processor variants were tested:

(1) E2160 L2
(1) E4500 M0
(1) E5200 R0
(1) E6400 B2
(4) E6600 B2
(1) E6850 G0
(6) Q6600 G0
(1) Q6700 G0
(1) E7200 M0
(1) E8500 E0
(3) Q9650 E0
(6) i7 920 C0
(1) i7 940 C0

Of these 28 individual processors, 17 of which are quads, my findings show that the Analog Thermal Diode is typically linear from low idle temperatures thru very high load temperatures. Testing also revealed that the 5c Gradient between CPU temperature and "Mean" Core temperature is relatively constant from 4c to 6c, which conforms with the detailed thermocouple testing performed by rge.

The most interesting point is that when you originally conducted your IR testing, except for a few low order variables concealed from your Fluke IR gun on the IHS, apparently you were closer than you may have since thought. For example, the Core 2 processors which I've tested that are suposedly Tjunction Max 100c have shown values that average from 97c to 98c, with the exception of the i7's, which are nearly spot-on between 99c and 100c.

As such, it's likely that the differences often seen in the Core 2 quads between each pair of dual cores is 100c and 95c, which yields a Mean Tjunction Max value of 97.5c. This obviously coincides with my findings, and offers further insights toward Intel's new term "Tj Target".

Comp

After nearly three years of work on this topic, it's difficult to consider that I've somehow misinterpreted the fundamental principals. Come to think of it rge, you and I had this CPU temp versus Tcase discussion at Tom's probably a year and a half ago. Regardless, whether the the CPU to Core gradient is actually between 3 to 7c among the processors we've collectively sampled, we're down to splitting fine hairs on this, because we're all within a few degrees.

Comp