Re: Vertical Beam Interrupt on VGA

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#3869

From: Niilo Neuvo
Date: Wed, 12 Dec 1990 04:47

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The code is 100% ok. It is just the fact that most of the current
VGA card don't support the horizontal retrace interrupt. When IBM
made it's original VGA card for the AT it didn't support interrupts,
so most vendors decided that they don't have to support it either.
(I read this from a book called programming IBM EGA/VGA, can't
 remember the author(s) nor the publisher.)

The IBM PS/2 series supports the interrupt as fasr as I have tested
(and read).

You have to work around this problem by polling the CRT interrupt bit.
I have never tried syncing the timer to the raster, but I guess
that it could be done rather easily with a bit of programming.

--
      NN   NN  NN   NN  NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
    NNNN    N  NN    N  NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
  NNNNNN  N    NN  N    NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
NNNNNNNN  NN   NN  NN   NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN

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References: <2135@ccadfa.adfa.oz.au>

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!mit-eddie!bloom-beacon!eru!hagbard!sunic!news.funet.fi!tut!nn86302
From: nn86302@tut.fi (Niilo Neuvo)
Newsgroups: comp.os.msdos.programmer,alt.msdos.programmer
Subject: Re: Vertical Beam Interrupt on VGA
Message-ID: <NN86302.90Dec12054731@uikku.tut.fi>
Date: 12 Dec 90 04:47:31 GMT
References: <2135@ccadfa.adfa.oz.au>
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Organization: Tampere U of Technology, Finland
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In-Reply-To: bcf@ccadfa.adfa.oz.au's message of 11 Dec 90 02:57:27 GMT

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