GA8KNXP REV1 P4 3 GHZ overheating

Hi
My GA8KNXP Rev 1 P4 3 Ghz Bios F13 has just developed an issue where
the CPU is getting very hot approaching 70C.
The CPU Cooler is working, have removed the cooler cleaned it ( it
was not very dirty) and reinstalled it.
I restarted the system and the temp was still about 70C.
I have disabled hyperthreading and the temperature is back down to
normal about 31C.
Motherboard monitor is installed and noticed the Core 0 voltage is
1.57V and the Core 1 Voltage is 2.75V.
I would have thought both cores should be the same voltage?
I am looking for help as to whether the Mainboard / CPU or both have
a fault?

Regards
Denis