James Sweet wrote:

I have one PC that will lose or gain hours at a time if the machine goes
into standby, another that does ok but still drifts enough that I have
to use a utility to keep it in sync with the atomic clock. On the other
hand a Sun workstation that I fire up occasionally to play with keeps
excellent time, even after sitting unplugged for 6 months it's usually
within a few seconds but then it was originally $25K.

The only PC motherboards I've seen that consistently kept accurate time
all had Dallas clock chips in them, and some of those chips were still
running properly from their internal lithium cells (permanently
encapsulated) 10 years later.