CPU Underclocks itself (EIST and C1E Disabled)

My CPU core 2 duo e8400@3.0ghz but it shows on post that is runs on 2.4 ghz, it would also show in cpu-z that it runs on 2.4 ghz, i have already turned off EISTS and C1E, I also manually clocked the fsb to 333 multiplier x9 but it would still go back to 2.4ghz, it would take a few reboots to my pc to make it run to 3.0ghz but it would then go back to 2.4ghz

i suspect the PSU to be the culprit because i would sometimes get random hangs and freezes.

but is there any case that a faulty PSU could make a cpu underclock itself? or the CPU itself is faulty

It would also take a few clicks to the power button to turn on my PC

MY rig is:
HEC Winpower 550watts
E8400
galaxy Gtx 260+
2x2gb G.Skill PI DDR2-1100
ASUS P5Q PRO TURBO

I'd go back and recheck BIOS to make sure your settings are saved on exit. That motherboard powers on in a funny way after saving new BIOS settings or unplugging the PSU and it's the same way with many Asus P5Q motherboards - it's normal. Don't hit the power button twice, just wait about a secind or two.

Have you tried a newer BIOS?
Maybe it's an early BIOS bug. Just guessing.

Check your Windows Power Settings. Sometimes that can override it. If its on the in between one you want to set it to performance.

Even though the E8400 has been supported by the P5Q (it is a P45 chipset after all made for the 45nm CPUs) I would make sure you have the latest one on it as it normally will resolve bugs as well as make sure that newer steppings are supported too.

So my suggestions are to check your Windows power settings, update the BIOS and as a last resort test the PSU.

BTW, what are your temps? A CPU will underclock itself if it gets too hot and after a certain time it will shut the PC down.

But how you disable it in the BIOS it seems to be premanent feature or in otherword how we enable to access it ?