Xref: utzoo comp.os.msdos.programmer:2352 alt.msdos.programmer:2299 Path: 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: Date: 12 Dec 90 04:47:31 GMT References: <2135@ccadfa.adfa.oz.au> Sender: news@funet.fi (#News ) Organization: Tampere U of Technology, Finland Lines: 20 In-Reply-To: bcf@ccadfa.adfa.oz.au's message of 11 Dec 90 02:57:27 GMT 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