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Why aren't computer clocks as accurate as cheap quartz watches?
writes:
Why do the battery powered clocks in personal computers tend to keep
worse time than quartz watches, even the $1 ones?
Apparently accurate timekeeping is still not a priority for
motherboard manufacturers. My old HP Vectra XU keeps very good time,
but it's an exception to the rule (in the days when it was built, HP
had a reputation for precision).
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 clocks are inaccurate to begin with; the small variations in case
temperature are not the source of inaccuracy. The clocks are very
consistent in their inaccuracy--in other words, they keep good time,
but they keep the wrong time, because they are inaccurately calibrated
at the factory.
The problem isn't limited to PCs. I recall mainframes that were off
by minutes per day. Surprisingly, for a very long time, most
computers were not equipped with any kind of useful real-time clock,
and many operating systems "estimate" the correct time based on
internal dispatch timers and things like that, which are invariably
very inaccurate. PC operating systems have traditionally done this,
too, because originally there was no RTC, and there has never been a
standard, high-accuracy, high-resolution RTC in PCs.
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