BIOS disappears

I'm putting an EIDE drive in a 7-year-old server, which has SCSI disks from that time -- still working, but they're very small.

There's only one startup setting I need to change:

I hit "delete" to enter the "CMOS Setup Utility".

I go to "BIOS Features Setup".

The setting I need to change is "HDD Sequence SCSI/IDE First".

I need to set it to SCSI, which is still the boot drive. The default is IDE ... the shop that made the server didn't need to change this, because there were no IDE drives ... they should have, but oh well.

But, inexplicably, sometimes, the system doesn't boot up properly. What's up?

Oh. 7-year-old server. The little CMOS backup battery is dead. I've been turning the machine off at the power strip, and it doesn't get the 3 volts it needs to keep my one change to the BIOS ...