After playing around with it for a while I checked the temps again. The CPU was at a nice and freezing cold - 48C and the water temperatures maxed out at 30-35C° after 5h of full load.
I found it a little bit weird that the temps didn’t change, no matter the CPU load. It stayed at a rock solid - 48C°, so I ran a log on both the CPU temp and water temp. The average CPU temp was -48C° and with - 47C° as a max, there had to be something wrong.
A few days later I sent Alex VanKaam (the guy that writes MBM) an e-mail about it and asked him if there were any known bugs at these low temps. He told me that he wasn't aware of any, and that it probably was caused by inaccuracy in the internal temperature diode in the CPU core or a combination of the former and a bug in the BE6-II. He also made me check if I used the correct sensors, and (unfortunately) I did use the correct ones.
This thing was really starting to get on my nerves, so I e-mailed ABIT about this problem and a few days later I got a reply from them confirming what Alex suspected. He said that it was a "common" problem at such extreme low temps and that he personally had tried to make a compensation-circuit for his own BE6-II without luck. What bugs me most is that the temps varied from -48C° and 0C° to 7C° after a reboot (It reads either NA or 66C° in BIOS). Now after a few calculations I found out that 0C° to 7C° was most likely the correct readout (and I was just about to slam my head in my keyboard).
Fig. 10 Motherboard Monitor readout
As you can see from the MBM screenshot, the CPU temperature is WinBond 2-P2 thermal diode, the system-temp is WinBond 3 and the external probe is WinBond 1.
Fine-tuning the TECs:
What’s important in any setup is to tune the performance to the max. In a setup involving peltiers, it’s a big advantage to use a variable power supply. This is because a TEC has an ideal-curve. If you’ve seen data for a TEC you know there’s a lot of parameters like Imax, Vmax etc. For fine-tuning a TEC you should alter the voltage until it cools max yet puts out a minimum of heat. If you don’t, a lot of power is wasted and you don’t get the as low temperatures as desirable. There are of course a lot of other factors involved in tuning the performance in a supercooler, but this will not be covered in this article.