Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!samsung!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: <776@csource.oz.au>
Date: 7 Jan 91 03:42:23 GMT
References: <773@csource.oz.au> <5188@trantor.harris-atd.com> <774@csource.oz.au> <1991Jan6.055747.7268@bronze.ucs.indiana.edu>
Distribution: comp
Organization: Unique Computing Pty Ltd, Melb, Aust.
Lines: 24

In <1991Jan6.055747.7268@bronze.ucs.indiana.edu> yawei@bronze.ucs.indiana.edu (mr. yawei) writes:

> >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.
                 ^^^^^^^^^^^^

> Doing an extra EOI is not a good idea. Yes, most of the time it probably
> doesn't show any ill effect, but suppose the timer interrupt comes on
> during another hardware interrupt, and you do an extra EOI...

... which is why I said "specific EOI".


> Worst yet, the timer interrupt has the highest priority, higher than
> hard disk, communication, etc., and can interrupt them all. Now we have
> a *potentially* serious consequence here.

None at all.

Regards,

 david