Hot take: swapping the dead CMOS battery in my old 486 fixed a weird boot loop

Wyatt Fisher · 2026-10-18T06:10:04.088913+00:00

Last Saturday I was in my garage in Boise poking at a 486 box I pulled from a thrift store for $15. It would post but then loop the RAM count over and over. I figured the board was toast and almost set it on the curb. Then I noticed the clock was stuck at 1994 every time and the BIOS kept losing the drive settings. I cracked open the case, found a crusty CR2032 from 1998 reading 0.4 volts, and swapped in a fresh one from the drawer. Booted straight to the hard drive first try and the RAM count settled. Cost me maybe 2 bucks and 10 minutes. Anyone else had a dead CMOS cell fake a bigger failure like this?

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Hot take: swapping the dead CMOS battery in my old 486 fixed a weird boot loop | Antique Tech Support - HW Forums