I have this system running at 333MHz but when I bought the computer years ago it was sold to me as running at 667 MHz. After a lot of formatting and changes I am now running Linux but wondering if I can get it back to the original speed. I suspect it was sold to me overclocked.

A pentium II sytem would not overclock by 100% so you have a pIII. Change your fsb in the bios back to 133 as it is running at 66 now.
66 x 5 = 333
133 x 5 = 667

Seems as though your cmos battery was removed or died and thats why you lost your bios settings.

Have you changed any of the BIOS settings? Are you even sure that you have a 667MHz CPU? You *may* have a 500MHz that was overclocked to 667MHz. There were no 333MHz P3's. It could be that you somehow lowered the FSB to 66MHz.

Do you have a manual for the board?

http://download.aopen.com.tw/Defaul...

I doubt that it was sold to you overclocked. P3-667s were pretty common. For some reason, your board just dropped down to the 66MHz bus setting. Weak CMOS battery, perhaps?

Switch it back up to 133MHz.

The creme de la creme of Socket 939:
Opty 185 @ 3.2GHz
SLI'ed GTS-640s, both flashed to 625/1458/1950
4GB PC3200
Blu-Ray/HD-DVD, X-Fi
A8N32-SLI Deluxe
3DMark06: 13896

Thanks for all the above responses. I switched the CPU clock frequency back to 133.3 MHz. Now it runs at 667 MHz. The clock ratio is at 3.5. There are some higher choices of the frequency available. Will it be safe to turn it up even higher?

"The clock ratio is at 3.5"

It has to be at 5.0 in order to run the CPU at 667MHz (133x5=667). Of course, the P3 has a locked multiplier, so it probably doesn't matter what setting the MB shows.

"Will it be safe to turn it up even higher?"

Probably. On a 133MHz FSB system, 150MHz is often considered to be the safe maximum bus speed. This will give you 150x5=750MHz.

Of course, many systems will go even higher than 150MHz. It doesn't hurt to experiment. I've got my P3-1400 system running at 158MHz (for a core clock of 1.66GHz) completely error-free.

The creme de la creme of Socket 939:
Opty 185 @ 3.2GHz
SLI'ed GTS-640s, both flashed to 625/1458/1950
4GB PC3200
Blu-Ray/HD-DVD, X-Fi
A8N32-SLI Deluxe
3DMark06: 13896