dmurdoch@watdcsu.waterloo.edu (D.J. Murdoch - Statistics) (10/28/88)
I just bought a Microsoft bus mouse for my XT clone. (They're offering an excellent educational discount.) When installing it, I found that the only interrupt line I had free was IRQ2, which is listed as conflicting only with an EGA and a network adapter. I don't have any plans to get a network adapter, but would like to upgrade from monochrome to colour. Does the VGA also use IRQ2? If so, is it possible to double up devices on IRQ lines without killing everything? Thanks for any help. If it's email'd, I'll summarize and post. Duncan Murdoch
chasm@killer.DALLAS.TX.US (Charles Marslett) (10/30/88)
In article <5206@watdcsu.waterloo.edu>, dmurdoch@watdcsu.waterloo.edu (D.J. Murdoch - Statistics) writes: > I just bought a Microsoft bus mouse for my XT clone. (They're offering an > excellent educational discount.) When installing it, I found that the only > interrupt line I had free was IRQ2, which is listed as conflicting only with > an EGA and a network adapter. I don't have any plans to get a network adapter, > but would like to upgrade from monochrome to colour. Does the VGA also use > IRQ2? If so, is it possible to double up devices on IRQ lines without > killing everything? ... > Duncan Murdoch The IRQ2 line is not driven by the IBM VGA card or several of the VGA clone cards (including older VGA Extra/EM cards from STB) -- other VGA clones do drive it (including the older VGA Extra and current VGA Extra/EM cards from STB) so as to be more compatible with the motherboard VGA on PS/2 computers. Normally, the difference is moot unless you run software that enables the display interrupt since the line is an open collector output through a resistor (should I say, usually -- nothing being for sure in this industry :-). If you get trash on the screen when moving the mouse or if you get spurrous mouse movements when you change the screen features (often color palettes or turning on or off the screen border) you will know the software you are using is playing with the EGA interrupt. Even in the worst case, the line can be cut in the EGA/VGA card (probably voiding your warranty ;-) and there will be no conflict other than losing the feature I just mentioned (you'll probably get more "snow" on the screen when you run programs that play with the palette a lot and do not use the BIOS or wait loops). Charles Marslett Chief BIOS fiddler STB Systems, Inc. <-- apply all standard disclaimers chasm@killer.dallas.tx.us
jack@csccat.UUCP (Jack Hudler) (10/31/88)
In article <5206@watdcsu.waterloo.edu> dmurdoch@watdcsu.waterloo.edu (D.J. Murdoch - Statistics) writes:
<I just bought a Microsoft bus mouse for my XT clone. (They're offering an
<excellent educational discount.) When installing it, I found that the only
<interrupt line I had free was IRQ2, which is listed as conflicting only with
<an EGA and a network adapter. I don't have any plans to get a network adapter,
<but would like to upgrade from monochrome to colour. Does the VGA also use
<IRQ2? If so, is it possible to double up devices on IRQ lines without
<killing everything?
<
<Thanks for any help. If it's email'd, I'll summarize and post.
<
<Duncan Murdoch
The EGA or VGA doesn't use the IRQ2 unless you enable it.
So to answer your question is use the IRQ2 interrupt for
the mouse, odds are that even if some program enabled it
the EGA/VGA Vertical Retrace interrupt would interrupt only
once and without something out there (i.e. program) to
re-enable the Vertical Retrace Interupt it would not
present a significant problem.
--
* OS2, what DOS should have been!