OK, some more A64 results.
First the test details: The motherboard is Abit KV8Pro. I disabled both CnQ and Abit EQ (messes with fan voltages), just left the "turn off PC if CPU is 85C" on.
I had to do the tests twice. The first time around the case door was open as the PSU I was using was a temp one (the installed-with-much-time-and-effort Antec 380s was unstable) sitting outside the box. Plus, I thought I could just change the multiplier and run the tests again without waiting for the CPU to cool properly. Wrong. It messed up the results. The second time round, I reconnected the Antec PSU (it takes some time for it to become unstable), closed the case door and properly cooled the CPU in between.
The PSU is modded with an acoustifan with the thermistor intact. Plus, the PSU has its own voltage adjustments. However, I used the rpm line to make sure that the fan rpms also stablized before taking any readings.
I used a freshly installed Windows 64bit edition. I was planning on using the BurnIn64 - a 64bit load program that does some fast fourier transforms but tests revealed that the K7 CPU Burn program loaded the CPU more and faster. On the average, it took 30 minutes for the CPU to reach steady state. I used ClockGen to lower VCore to allow faster cooling but readjusted VCore and waited at least 5 minutes before attempting another burn.
I used my own excel table (Russ's hadn't been posted yet), included the VCore readings from MBM as well. I used Excel's "add trendline" function to get the best fit.
I used a FSB of 200 (mobo doesn't allow lower) and used clockgen to change multiplier between 10 and 5 in 0.5 increments. Those are the limits of the BIOS. I wanted to try faster FSB but at 2000 MHz @ 1.5V the CPU hit 84C, 1C less than shutdown temperature so I didn't try.
When plotted, the points form a very nice line. Intercept point was 3.205C. Excel says there's a good fit with R2 = 0,9979.
Formula: y = 0.0221x + 3.205 where x is frequency, y is delta temp
Unfortunately, in the university I had a VERY picky professor who introduced us into technical drawing and I've become perceptive of small curvatures. And this line had a very slight curvature. So I tried a polynomial trendline to see what I would get. The polynomial trendline fit almost perfectly with an R2 value of 0,9998. The x2 factor was in the 1/million range which is why it looked straigt. With the new trendline, intercept became 11.958.
Formula: y = 0.000004x2 + 0.0105x + 11.958
So now, what is my calibration? +3.2C or +12C?
/Surgeon general's warning: Too much math mugs your brain /