From my experience, there is a possibility that installed software
contributes to the PC clock inaccuracies.
After experiencing task bar clock differences with real time on my new
Gateway PII, they instructed me to format a bootable disk (FORMAT A:/S) at
C:\, then use DOS "TIME" command to set the clock for the current time, and
let the system sit at the C:\ for a period.  I did it overnight, and the
next morning seletec "TIME" again and there was no difference with actual
time.  I have not determined which software application is intefering with
the PC clock, but know that the quartz clock retains accurate time.

John Penasack
-----Original Message-----
From: Earl Truss <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, February 09, 1999 4:51 AM
Subject: [PCBUILD] Why does my PC make such a poor clock?


I've been asked to explain why the current time shown in many applications
is often so far off from a wall clock - often losing or gaining several
seconds a day.  I was wondering if someone could point me in the direction
for a fairly technical reference.

I once read a magazine article about this but can no longer find it.  It
was written in DOS days and I believe their primary reason was because the
PC reads the current time from the real-time, battery-backed-up clock at
startup but then the operating system maintains the time from the timer
interrupt which is unreliable.  Here's where my memory fails me.  Could
someone fill in the gaps ... Why is this interrupt unreliable?  Is it a
matter of the clock signal varying or is it just poorly synchronized with
real-time?  Where do the clock signals for the various components - CPU,
bus, real-time clock, etc. - come from?  I don't have an extensive
background in basic electronics but do know quite a bit about the theory of
how a computer works at this level.  I think I could understand a pretty
detailed discussion of this.  I'd really appreciate it if someone could
help me out in the next couple of days.  Thanks.

                         PCBUILD's List Owner's:
                      Bob Wright<[log in to unmask]>
                        Drew Dunn<[log in to unmask]>

                         PCBUILD's List Owner's:
                      Bob Wright<[log in to unmask]>
                        Drew Dunn<[log in to unmask]>