I have a biostar 486 8433uud which has a ds12887a+ I changed it years ago can't remember what it had originally, regardless it works and has been working fine. I found some old ds1287 so decided to make a few coin battery mods.
I tried on 2 of them and both ds1287 give me the checksum error when booting. It doesn't give me low memory error just checksum errror restore defaults. Obviously I can't make any bios settings stick because this error comes on each boot.

I checked the battery it has a steady 3v, it is wired up correct. ds1287 is a direct replacement for ds12887a from what I read so it should be compatible?

There is really not much to wire and I checked my wiring it looks good. Yes I did disconnect the original ground on pin 16 and soldered negative to the disconnected ground on the bottom.

Anybody run into this issue before?

here is a picture