Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!munnari.oz.au!csource!david
From: david@csource.oz.au (david nugent)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Backgroup processing (Was Re: DOS idle interrupt (INT28))
Message-ID: <774@csource.oz.au>
Date: 6 Jan 91 02:08:03 GMT
References: <5094@trantor.harris-atd.com> <1537@netmbx.UUCP> <1990Dec19.050307.16450@engin.umich.edu> <1991Jan5.043055.17637@bronze.ucs.indiana.edu> <773@csource.oz.au> <5188@trantor.harris-atd.com>
Distribution: comp
Organization: Unique Computing Pty Ltd, Melb, Aust.
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In <5188@trantor.harris-atd.com> sonny@charybdis.harris-atd.com (Bob Davis) writes:

> >Also, the PIC is rearmed by the time INT 1cH gets control, so you don't
> >have to fiddle around with EOI's at all.  It's an "ideal" place to pop-up.

> Are you sure that the PIC is rearmed? 

Whoops, did I say that?  :-)

You're quite right.  The "correct" thing to do is to call the original
INT 1cH handler, rarm the PIC with a specific EOI and enable interrupts.

I actually found it was rearmed in some situations and others not. This
is probably a function of BIOS versions, DOS versions and/or prior INT 1cH
handlers. But I've never found a situation in which there's a problem with
doing another specific EOI just in case.

 david