Motherboard or PSU problem?

[GFORCE100]

Hello,

Complete PC specifiation can be found below:

I'm looking for a second opinion regarding the following:

I have a system with an overclocked Prescott-2M (3.73GHz EE) at 4.16GHz at default Vcore that runs at 4161MHz when idle in Windows XP. If I start anything power intensive such as an Nvidia 3D demo or SuperPi, and refresh thus check CrystalCPUID readings that confirm the CPU is slowing down by around 200-300MHz does this mean that:

a) The motherboard cannot sustain enough stable current thus the CPU is forced to run slower. In such case the FSB is slowed down as a result of lack of steady current.

or

b) The PSU is struggling thus provides less power to the CPU which in turned is forced to slow down.

or

c) Both a) & b)

System specification:
Asus P5AD2-E Premium motherboard
Crucial Ballistic PC6400 DDR2 RAM
BFG 7800GTX
2x SATA HDD's
1x Optical drive,
1x PCI TV/Radio card
Enermax 550PSU with 24A on +12V line
Default Vcore
1.6V chipset voltage
1.50V FSB termination voltage
Memory at 729MHz

Please note that the CPU is not throttling in any case explained herein as proven by ThrottleWatch 2.01 and the CPU temp is always 60C at most.

At 4.1GHz the CPU will always run at ~4100MHz leading me to think 4.1GHz in on the border line when the power drain on the +12V line is so high that anything higher causes the qualify of current to diminish. With this said the Asus probe still reports healthy voltages for each. I can very slightly remedy the problem above 4.1Ghz by improving on the Vcore or increasing the chipset voltage. Even with this we're talking an extra 30MHz. At 14x300 the CPU will never report above 4.17GHz in Windows and once SuperPI or similar is started it dips to around 3.7-4GHz.

Would appreciate others to comment.

Many thanks,

 

[redhatlinux]

I hate to tell this, but it could be either. The PS provides the power, but the mobo has the voltage regulators and capacitors. A PS that provides voltages with too much ripple, under load is a problem. Like wise voltage regulators that go slightly out of spec, or flimsey mobo caps will also create 'noise' on the voltage rails. Even a case with poor EMF/ESD shielding can be a problem as speeds get higher. Sometimes this is not an exact science, all components have operational tolerences, if you get a couple of components that are slightly off then the higher speeds are the first to show the problems.

 

[GFORCE100]

Thanks,

Any tests I can do to confirm either?

Perhaps if others who have this motherboard and have overclocked Prescotts on it above 4GHz could join in and tell their story.

The system is stable but as you say the PSU might be causing a larger ripple than OK at high speeds.