CMOS battery replacement
You are getting the dreaded 161 error code at boot, the date is off, and the floppy drive can’t read floppies anymore. All this because the CMOS battery is flat and needs to be replaced. Here’s how.
The following info is relative to the PS/1 2011, but should apply to Model 2121 as well.
The floppy drive of your PS/1 has broken down and you need a replacement. Unfortunately it has an IBM proprietary interface and you cannot use a standard floppy drive. This guide will teach you how to adapt and use a dirt cheap, standard 1.44MB 3.5″ unit (thanks to paperinik77pk)