[comp.sys.ibm.pc.hardware] Real time clock tuning.

torkil@psivax.UUCP (Torkil Hammer) (07/06/90)

My AT compatible has a calendar clock that is about one minute off per day.
This is annoying.  Can these clocks be tuned?

In contrast, my $30 wristwatch is accurate to within 1 minute per year.
Does anybody know why a computer clock can't be equally good?

Torkil Hammer

grege@gold.GVG.TEK.COM (Greg Ebert) (07/11/90)

In article <3440@psivax.UUCP> torkil@psivax.UUCP (Torkil Hammer) writes:
>My AT compatible has a calendar clock that is about one minute off per day.
>This is annoying.  Can these clocks be tuned?
>

Possibly. If there is a trimmer capacitor next to the 32.768 Khz crystal, try
tweaking it. If there's no capacitor, try replacing the crystal. If you're
lucky, your clock is running fast - try paralleling the crystal with a small
variable capcitor (say 5-50pf) and tweak it. If you aren't a hardware type, 
try writing a program which corrects the time by computing the elapsed time
since last reboot, apply a fix, and update the clock.