In response to a question from D & R on how to "zap" the CMOS on an old 486 computer, jesus.diaz suggested a crazy idea that had worked for him in the past: Use an electrostatic discharge to clear the BIOS. But as D & R reminded him, static electricity doesn't mix well with motherboards.
You needn't resort to such extreme (and yes, creative) measures to fix the problem, though. Put yourself in D & R's shoes. You are locked out of your old 486 computer and don't know the BIOS password. How are you going to clear the BIOS and gain access? The obvious answer: Remove the CMOS battery. But here's the catch—the battery is fixed to the motherboard. Now what?
Clear the BIOS by removing the jumper on the motherboard
Member Fenaikh suggests getting out the motherboard manual. It should diagram and describe the various jumper locations and settings. It should contain instructions on how to arrange the jumpers to clear the BIOS settings. But in D & R's case, the motherboard manual is nowhere to be found. Member randalbin reminded D & R: "On some motherboards, simply removing the jumper is not enough. In some cases, there are three pins and you must remove the jumper from 1 to 2, connect 2 to 3 for a few seconds, and then replace the jumper on 1 to 2." Knowing enough about the motherboard to proceed without the manual, D & R removed the jumper (for 15 minutes) and experimented with different settings.
This didn't clear the BIOS—strike one.
Disconnect the motherboard from the power supply
Tourist tech suggested removing the motherboard from the power supply for an extended amount of time. He said that capacitors within the power supply could hold a charge for the motherboard. To clear the BIOS, disconnect the motherboard from the power supply. Ideally, after this step, one would want to remove the CMOS battery, but as previously noted, the battery is fixed permanently to the motherboard.
D & R unplugged the motherboard from the power supply for 48 hours. The BIOS was still not cleared—strike two.
Flash the BIOS
"You may have to flash the BIOS. But, of course, to do that, you'll have to boot from a floppy," wrote computer systems engineer Maxwell Edison. Unfortunately, access to the A: drive was being blocked by the BIOS. D & R frustratingly recognized the conundrum.
It's a BIOS catch-22. To flash the BIOS, you must have access to the A: drive. And to access the A: drive, you must flash the BIOS. Edison pointed out that the boot order set in the BIOS is, most likely, C: drive first, A: drive second. The boot order can be changed (reversing the order, A: drive first, C: drive second), but doing so requires access to the BIOS Settings menu, which is password-protected. Edison puts forward the following solution. "Unplug the ribbon cable from your hard drive. That will force the computer to boot from the floppy."
"Excellent idea. I didn't think of doing it that way," replied D & R. This advice should prove to be a great sidestep for D & R's BIOS password problem.