Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!tut.cis.ohio-state.edu!cica!bronze!yawei
From: yawei@bronze.ucs.indiana.edu (mr. yawei)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Backgroup processing (Was Re: DOS idle interrupt (INT28))
Message-ID: <1991Jan6.055747.7268@bronze.ucs.indiana.edu>
Date: 6 Jan 91 05:57:47 GMT
References: <773@csource.oz.au> <5188@trantor.harris-atd.com> <774@csource.oz.au>
Distribution: comp
Organization: Indiana University, Bloomington
Lines: 18

In article <774@csource.oz.au> david@csource.oz.au (david nugent) 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...

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.

> david

yawei