Newsgroups: comp.os.os2.programmer
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uunet!dialogic!gerry
From: gerry@dialogic.com (Gerry Lachac)
Subject: Re: Sharing Interrupts on a PS/2
Message-ID: <1991Jun03.150801.25038@dialogic.com>
Organization: Dialogic Corporation
References: <9105312050.AA16347@ucbvax.Berkeley.EDU>
Date: Mon, 03 Jun 91 15:08:01 GMT

In article <9105312050.AA16347@ucbvax.Berkeley.EDU> klos@bcrvmpc3.vnet.ibm.com (Marty Klos) writes:
>
>According to the book (see note *):
>  "POSITION RULE An interrupt handler that shares an interrupt level
>      must not depend on its position int the list of handlers for that
>      interrupt level."
>
>My interpretation is that the order is undefined.  Unfortunately,
>this does not help you predict how long after an interrupt occurs
>before a particular interrupt handler gets control.

Agreed.   After looking into this furthur, running some tests, setting
some breakpoints (and looking at the IBM docs - thanks :-), it seems
to me that the interrupt handlers are called at seemingly random
times.  I would venture to guess that maybe the interrupt routines are
called in some round-robin manner for performance reasons.  That seems
reasonable to me.

In level-sensitive mode, the 8259 interrupt controller locks out the
interrupt level if a number of spurious interrupts are received.  Is
it possible to alter this number or disable this feature under OS/2?



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