Wierd problem- CPU severly underclocks self

One of my older rigs felt slow, and I had been running it at stock speeds for awhile (I had overclocked it previously, but I reverted it when I reformatted to Win7). I fired up CPU-Z, said my CPU speed was 750 MHz (at load). Rather miffed.

It's an AMD Athlon X2 4800 in an old crappy AM2 mobo, ECS 6100 GeForce.

Stock its 200x 12.5= 2.5GHz
Now it runs at 55 x 12.5=750 or so MHz (according to CPU-Z, says everything is fine in BIOS)

I think it might be my motherboard going senile. Previously, it would give me 10x multiplier when set at 13x (12x was fine).

Bios still says 200 bus clock.
I've cleared CMOS. Didn't work.

I'm going to leave it hard off for a night, sometimes that works on old systems for some reason. Preparing to flash the BIOS once I find a damned floppy drive and floppy.

The GPU is a Radeon 4870 if that has anything to do with it.

EDIT: AMD's Cool and Quiet has been turned off (EIST?)

EDIT 2: 4th reset is the charm. Somehow works again for no apparent reason? I'm confused.

I would check the cMoS backup battery and the power supply output voltages but it surely sounds like you have a need for new hardware in the not too distant future.

As above i think you Bios battery might be dying or yuor board isnt drawing enough power try if you have a different board you can test the cpu in i would do that

energy saving feature. depending on your bios there may be one, or up to 3 things to fully disable it all.