Subject: Re: How to tweak clock rate
To: None <current-users@NetBSD.ORG>
From: Dave Huang <>
List: current-users
Date: 03/30/1998 09:39:44
On Sat, 28 Mar 1998, Ken Hornstein wrote:
> I have heard of people that replace their clock crystal with one more
> accurate (10 ppm is a figure I've heard).  It's my understanding that
> the crystal you want to replace on the i386 is the one used by the PIT,
> which should be something close to 14,317,180 Hz.  Of course, that
> assumes the crystal in question is socketed, or you're handy with a
> soldering iron ...

Hmm... interesting idea... the crystal (14.318180 MHz) isn't socketed
though. I'm pretty good with soldering (was bored and took a surface
mount soldering class at the local community college :), but I'm
probably too lazy to change the crystal :)

> Since presumably your biggest problem is that your clock crystal
> isn't exactly what it's supposed to be, you could try defining a
> new value for TIMER_FREQ (/sys/arch/i386/isa/timerreg.h), based on
> your calculated time drift.  This calculation should be straightforward,
> but since it's late, I don't feel like doing it :-)

Ah... a software fix :) Much more convenient if it works, and it looks
like it does... I increased TIMER_FREQ from 1193182 to 1193732 and now
the clock only gains ~150ms in 2hrs. Maybe I'll try increasing
TIMER_FREQ by another 25 or so. Thanks for the tip! :)
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