8NPA-SLI and F71872F temp sensors

I've got a 8NPA-SLI socket 754 motherboard. It uses the F71872F i/o
chip and it has three temp sensors that read out in SpeedFan: Temp1,
2, & 3.

Temp1 appears to be the motherboard cpu temp sensor (not the core).
Temp2 appears to be the motherboard ambient temp.
Temp3 is the one that's confusing me. It's reading 84C min to 96C
max, typically ~92C idle.

Wondering if anyone knows what that 92C Temp3 is. I'm thinking it's
either the X1300 GPU temp or the nforce4-SLI chipset temp.

I also notice the cpu temp sensor reads 15C min, 32C max, but the
core temp is 30C min and 45C max (venice E6 stepping). I'm
wondering if that's because I haven't loaded the AMD cpu driver or
if there's that much difference in temp at the cpu socket sensor.
My older clawhammer cpu seemed to get accurate readings from the
motherboard cpu sensor (37C-52C range).