Vcore fluctuations?

[Propilot]

When I am running under a load (Prime95 torture) on my 2.8c, I have the Vcore set at 1.67v.
But when I check it thru cpu-z, it drops down to 1.59-1.61 volts (avg. 1.6).
This is on a Antec 400w supply.
My system is semi stable, but was wondering if this could be a problem and I need to up the power supply.

My setup is:
P4 2.8c @ 3.5
P4P800 deluxe
1g DDR3200 at 1.85v (2-2-2-5)
Geforce 4
3 WD hardrives
5 case fans
Zalman cooler

Thanks

[Propilot]

Just did some more tests.
Power was at 1.625

Under load lots of fluctuations. The lowest went to 1.53 volts.

[larva]

This degree of fluctuation in the Vcore is essentially normal.

You need to get a voltmeter and measure the 12V output from the power supply at stock cpu voltage and clock rate. Then do it again overclocked. If you see a sharp drop in the 12V line from the overclock you need to upgrade to a stronger supply. If this is the case a new supply should reduce the Vcore fluctuations to an extent, but they will never dissapear completely in any event.