Replaced the Dallas 12887 RTC on this ASUS P/I-P55T2P4. Now it doesn't POST with dual voltage (2.8 vcore) CPUs such as MMX 166 and 233. 3.3v P133 and P200 CPUs still work.
Real-time clock - Wikipedia
So I tried fixing the Dallas ds12887a RTC on my aOpen ap53 motherboard. It didn't go over so well... : r/retrocomputing
What Are Real-Time Clock Chips? | RTC Chip | Basics
Amazon.com: BZBYCZH CMOS RTC Battery Compatible for Asus G550JK CMOS BIOS RTC Battery : Health & Household
Desktop Motherboard RTC Circuit FIX With Diagram - YouTube
Are there different types of CMOS batteries? - Quora