In article . com,
says...
Why do the battery powered clocks in personal computers tend to keep
worse time than quartz watches, even the $1 ones?

The computer batteries measure fine, at least 3.15V.

I thought that the problem was temperature swings in the computers
(25-38C), but a couple of cheapo watches taped inside the computers
kept better time.

The short answer is that computer makers don't care.

More specifically, even cheap watches usually have a trimmer
capacitor on the timebase crystal that someone actually adjusts.
Computer makers usually choose to save pennies by using a fixed
capacitor and not having to pay labor to adjust.