Strictly it is called "CMOS Reset." You do it with jumper J21 on the lower back portion of the motherboard, at least on an S2460 (see the Tyan site for a manual if that is not the one you are using). Power down and disconnect the power supply, move the jumper from pins 1 and 2 to pins 2 and 3, wait about three seconds, and then close pins 1 and 2 again. Power up and reconfigure the BIOS.

This may work or not, but it has for me on those occasions when nothing else seemed to work. That was on a Tyan S2460 and S2663. My K7X Pro has never needed this, but it is straight SCSI other than an IDE DVD.

I agree with the comment suggesting use a live CD. I prefer FreeSBIE, but then I'm a BSD guy.