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From: nmurrayr@cc.curtin.edu.au (Ron Murray)
Newsgroups: comp.music
Subject: PC MIDI board IRQ lines
Message-ID: <1991May31.154138.8527@cc.curtin.edu.au>
Date: 31 May 91 07:41:38 GMT
References: <10855@jarthur.Claremont.EDU> <oNco32w164w@midiline>
Organization: Curtin University of Technology
Lines: 28

In article <oNco32w164w@midiline>, knid%midiline.uucp@elroy.jpl.nasa.gov (Vermicious Knid) writes:
> The new update for Master Tracks Pro is now shipping.  It is version 3.93 
> and runs under Windows in real, standard or enhanced mode, although in 
> enhanced on a 386, you must change the IRQ for your MIDI card from 2 to 
> something else, like 5 or 7, due to the fact that Windows in enhanced 
> mode redirects IRQ 2.

   It seems to be a little-known fact, but on the PC and clones, IRQ 2 is used
by EGA (and above) as the frame interlace interrupt. Thus MIDI software written
for these machines may or may not work on EGA, VGA etc. (although CGA will be
OK as a rule). The actual results you get depends upon which line driver in
either the MIDI board or the video board is stronger: if the video board wins,
you don't get any MIDI interrupts. If the MIDI board wins, you only get half
the screen lines (and the display can look quite weird!).
   It would seem to be an idea to encourage MIDI software writers in general
to allow selection of the IRQ line: most of the early ones didn't, and I spent
ages changing them manually). Perhaps the situation has improved: I haven't
looked for a while.
.....Ron
-- 

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