Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!vsi1!hsv3!jls
From: jls@hsv3.UUCP (James Seidman)
Newsgroups: comp.windows.ms
Subject: Re: 1024x768 Interlaced Monitors
Message-ID: <4154@hsv3.UUCP>
Date: 29 Aug 90 20:45:57 GMT
References: <1804@abvax.UUCP> <4173@tuminfo1.lan.informatik.tu-muenchen.dbp.de>
Reply-To: jls@headland.UUCP (James Seidman)
Organization: Video Seven / Headland Technology
Lines: 26

In article <4173@tuminfo1.lan.informatik.tu-muenchen.dbp.de> rommel@lan.informatik.tu-muenchen.dbp.de (Kai-Uwe Rommel) writes:
>Flickering does not only depend on interlaced/non-interlaced method but
>much more on the screen redraw frequency. It should not be below 60Hz. I
>have a Paradise VGA-1024 and it operates in 1024x768 (interlaced !) with
>a gray-scale monitor absolute flicker-free. If you move close enough to
>the display, you can see that once only the odd and then only the even
>scan lines are painted. But thats not the "flickering" you mean, I
>assume. The Paradise VGA-1024, for example works with 89Hz (!) repaint
>frequency in 1024x768 mode.

But your redraw rate is effectively half that, i.e. 44.5 Hz.  Because of
the interlacing, only half of the lines on the screen are drawn on each
pass.  You card *has* to use at least 89Hz... if it used 60, then it would
look about as good as a non-interlaced display running at 30 Hz.  That is,
terrible.

It is true that refresh rate is important.  However, most cards which do
interlacing run between 88 and 96 Hz.  Perhaps more important is the
persistance of the phosphor on your screen.  That's how IBM gets away with
it on their 8514/A... you hook it up to an 8514 monitor, which has *VERY*
long persistance phosphor, and you see almost no flicker at all.  But hook
it up to, say, a Nanao 9070S, and you've got an unusable display.
-- 
Jim Seidman (Drax), the accidental engineer.
UUCP: ames!vsi1!headland!jls
ARPA: jls%headland.UUCP@ames.nasa.arc.gov