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Date: Tue, 29 Jan 2002 15:39:11 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
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To: Babu Kalakrishnan <kala AT sankya DOT com>
cc: djgpp AT delorie DOT com
Subject: Re: DPMI Interrupt latency ?
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On Tue, 29 Jan 2002, Babu Kalakrishnan wrote:

> Tried the way you suggested - but it doesn't seem to work if I try
> invoking the hardware interrupt through a software (INT XX) call. I
> hooked INT0D (IRQ5) from protected mode. But on reaching the shell, The
> interrupt vector of Int 0d was pointing to the initial Real mode value
> in ROM. I then tried calling Int8D (where the master PIC vector seemed
> to be redirected to), but still my interrupt handler didn't seem to get
> called. Does the code check if the interrupt is a genuine hardware IRQ
> and skip calling the handler if it isn't ?

AFAIK, only hardware interrupts are reflected to protected-mode 
handlers.  Software interrupts don't get reflected.  It's in the DPMI 
spec.  (There are a couple of software interrupts, listed in the DPMI 
spec, that are exceptions.)