Date: Thu, 20 Feb 1997 10:42:46 +0100 (MET) From: Søren Schmidt <sos@ravenock.cybercity.dk> To: brian@awfulhak.demon.co.uk (Brian Somers) Cc: hackers@FreeBSD.ORG, brian@utell.co.uk Subject: Re: Screen flickering Message-ID: <199702200942.KAA02525@ravenock.cybercity.dk> In-Reply-To: <199702200150.BAA11591@awfulhak.demon.co.uk> from Brian Somers at "Feb 20, 97 01:50:00 am"
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In reply to Brian Somers who wrote:
> I've just set up FreeBSD (~-current) on a laptop, and to my surprise,
> *everything* works - apm, pcmcia (3c589c doesn't hang), audio, cd, X
> - well done guys....
>
> There was only one small problem - it's now fixed (avoided), and I'm
> starting to wonder if I've been seing this problem for a *long* time
> on my main machine (and just assuming I have a dodgy monitor).
>
> Essentially, the syscons screen "flickers" probably every couple of
> seconds on average, and only with "vidcontrol -c destructive". From
> what I can figure, the "while (!(inb(crtc_addr+6)&8)) ;" bit in
> syscons.c doesn't work as expected (although removing it makes
> things a *lot* worse)....
>
> Is anyone actively responsible for this code ? Or is it worth my
> while to delve deeper ?
Yep, syscons is my baby, and I know of this problem, it is not
easily fixable however :(
The problem is that reprogramming the chargen produces "noise"
on the screen, thats the reason for trying to do the update in
the vertical retrace period. The busy loop is actually REAL
bad news in a timeshare environment, but there is not much else
to do. The problem you are seing is probably due to an interrupt
getting in the way of the normaly hidden update..
> FWIW, the laptop has a Chips & Tech 65545 chipset. My main machine,
> which hasn't flickered yet, has had both a Hercules Graphite
> Terminator and a #9...... oops - just got a flicker in single-user
> mode :( Guess it is a lousy monitor after all :(
Hmm, the problem is present on all videocards, except a few that
can update the chargen without flicker. But in any case a good
stable monitor will certainly hide the problem...
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Søren Schmidt (sos@FreeBSD.org) FreeBSD Core Team
Even more code to hack -- will it ever end
..
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