unclewebb - thanks for your response (and your neat program)....I really appreciate it.

Regarding the CPU temp that's reading 20C (Tcase), I thought this sensor was located on the case of the processor but read by the motherboard?

I opened the case, turned up the exhaust fans to max (they're Antec Tri-Cool fans) and underclocked/undervolted my system and the min temps are:
- CPU: 16 C (definitely not believable)
- Cores 0-3: 31 / 28 / 40 / 40
- Ambient: 23 C

If I run your "Test Sensors" test, Core0 and Core1 both bump up by about 4 C and come back equally fast. So, it looks like Core0 and Core1 are decent although slightly offset from each other.

Since my CPU sensor seems to be inaccurate, I guess I can use Core0 and Core1 as my reliable measuring sticks, right? And since Core2 and Core3 appear to become unstuck and roughly track the others when > 40 C, I guess I can trust all 4 in those circumstances? What would you recommend for calibration factors?

Are the temp sensors any better in the Xeon equivalent 45nm Quads? I'm just curious because I have to build a few more boxes like this one....