* Varta barrel battery, subject to leaking and corroding traces
* AA/AAA style brick + leads to motherboard, easy to replace
* Dallas DS1287 epoxied battery + chip - can be replaced, cut into to tap directly into the chip, or replaced with Necroware's nwX287 RTC module [0]
* Lastly, the standard CR2023 style. I started seeing these appear in later 486 Socket 3 boards, very rarely on anything earlier
[0] https://github.com/necroware/nwX287
* Varta barrel battery, subject to leaking and corroding traces
* AA/AAA style brick + leads to motherboard, easy to replace
* Dallas DS1287 epoxied battery + chip - can be replaced, cut into to tap directly into the chip, or replaced with Necroware's nwX287 RTC module [0]
* Lastly, the standard CR2023 style. I started seeing these appear in later 486 Socket 3 boards, very rarely on anything earlier
[0] https://github.com/necroware/nwX287