P4C800 Deluxe Pescott CPU Troubles Further Information

I have been running a P4C800 Deluxe mobo with a 500W Shure PSU and a
2.8Ghz Northwood CPU. The other day I purchased a new P4P800S-X mobo
and 3.0GHz E (Prescott) CPU and an A-Open computer case featuring their
standard 300W power supply. This second machine is being built for my
mother-in-law. Both mobos are running the latest BIOS updates, 1017 in
the case of the P4C800 deluxe.

I decided to swap the 2.8GHz CPU that has been running flawlessly for
the past 10 months out of my computer into her new board, and I placed
the brand new boxed 3.0GHz CPU into my P4C800 deluxe board. I
immediately started to have problems. Firstly, on the first boot up,
the system shutdown instantly and completely as Windows XP was being
loaded. It was as if the power plug was pulled from the wall socket.
I restarted the system and checked all the BIOS settings, which
appeared to be fine (no overclocking) and this time the system booted
into Windows XP. However whenever the system is given a moderately
heavy workload, the system suddenly shuts down.

I installed ASUS probe into my system and watched the temperature of my
new CPU. The CPU runs at idle at 58 degrees Celsius using the stock
fan that came with the CPU in the box. Then when the load on the CPU
increases, the temp goes to about 61 degrees and then the system
instantly shuts down. I replaced the standard fan with a brand new
Zalman high performance fan designed for high performance processors,
and the temperature of the CPU temp at idle only went down by a degree
or two. The problem with the system suddenly shutting down remains
when the CPU has a moderate load.

I then swapped the CPUs back so that the 3GHz Prescott and standard fan
was placed into the brand new P4P800S-X mobo, and ASUS probe reports
the CPU as idling at 46 degrees C. Significantly cooler than when the
same chip and fan setup is placed into my P4C800 deluxe.

I can only guess that the BIOS on my P4C800 deluxe is not controlling
the chipset on the P4C800 deluxe mobo to supply the Prescott CPU with
the correct voltage, despite the fact that the board is flashed with
the latest BIOS update. The BIOS in the P4P800S-X handles the Prescott
CPU without a problem. I have run the new machine continuously running
a number of stress tests on the system and it has been rock stable.

The BIOS in both machines is set with the AI Overclock Tuner set to
auto, and CPU VCore Voltage set to auto.