On 26 Oct 2005 15:03:04 -0700 wrote:

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

There are 2 causes.

The first cause is that the internal clock (real time clock) on the
motherboard is a device which the motherboard manufacturer much buy
from someone else. They can buy this item in various degrees of
precision, but the cost goes up as you request more precision. Since
there is lots of pressure to keep cost down, but not so much pressure
to keep good time, the motherboard manufacturers don't press for
highly accurate real time clocks.

The second reason was explained by someone else. It's the fact that
the OS clock can fall behind the real time clock due to the way the OS
is written. This error is minimal when your computer is first booted
up, but it can become significant if it is left running for days. This
error is reset to zero each time you reboot.

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Jim Adney
Madison, WI 53711 USA
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