In Asus Probe one can find a CPU temp reading and a motherboard temp reading. Is the motherboard temp that of the northbridge? Southbridge maybe? Or just the board in general?

I have a thermal probe touching the bottom of the Thermalright NB-1 on the nForce4-SLI chipset. Asus probe reports about 2C lower than the thermal probe (right now 32C versus 34C). The temps are probably read close to the chipset. I wish I knew more, too...

I have an asus p4p800 deluxe

I don't think so. Otherwise, my alarms would always be going off (my northbridge heatsink is too hot to touch). I used to even have stability/crash problems due to northbridge overheating

For intel boards, they have 3 temps...cpu, mobo, and chipset. So I guess asus just drops the chipset sensor...

I think the mobo temp is just the mobo in general...sort of like the ambient temperature.

I have an asus a8n-sli deluxe, and the motherboard temp does not change when I stop (with my finger) the fan of the northbridge, and the sink gets painfully hot. It is not the NB temp, at least in my mobo.

Regards.