From owner-freebsd-hackers  Thu Jul  2 07:56:37 1998
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From: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
Message-Id: <199807021326.PAA12564@labinfo.iet.unipi.it>
Subject: Re: timeout granularity (was: Re: Console driver...)
To: smoergrd@oslo.geco-prakla.slb.com (Dag-Erling Coidan Smørgrav)
Date: Thu, 2 Jul 1998 15:26:10 +0200 (MET DST)
Cc: sos@FreeBSD.ORG, nick.hibma@jrc.it, hackers@FreeBSD.ORG
In-Reply-To: <rx4af6s2x80.fsf@oslo.geco-prakla.slb.com> from "Dag-Erling Coidan Smørgrav" at Jul 2, 98 03:33:48 pm
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> With a 70 Hz refresh rate, we're talking more like 14 ms in the worst
> case, which is pretty darn bad.
> 
> > If one can, say, assume that the vertical retrace is never less than
> > 1ms, then HZ=2000 should do the job (wakeup at every tick...).
> 
> Ah, I didn't think of it quite like that. Yes, it would work, and you
> wouldn't have to busy-wait at all; just wake up at every tick, check
> if you're in a retrace, and if you are, do your job.

actually, if you could only know how far away you are from the retrace
(perhaps by reading some status register ?) you could even tolerate a
coarser timer.

	luigi

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