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From: raymond@math.berkeley.edu (Raymond Chen)
Newsgroups: comp.os.msdos.programmer,comp.sys.ibm.pc.hardware
Subject: Re: How to find correct int #
Message-ID: <1991Jan21.050354.6199@agate.berkeley.edu>
Date: 21 Jan 91 05:03:54 GMT
References: <1991Jan21.013033.4574@cs.mcgill.ca>
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In-Reply-To: pedro@cs.mcgill.ca (Sandro MAZZUCATO)

In article <1991Jan21.013033.4574@cs.mcgill.ca>, pedro@cs (Sandro MAZZUCATO) writes:
>	I'd like to be able to write a small program to simulate the 2 
>possible sequences of keys [that change CPU speeds]
>I think that this triggers an interrupt in the
>BIOS... how can I find the right interrupt.....


Typically, they emit magic numbers out special ports.
Different machines do it differently.

The only way to find out for sure is to (ugh) trace through
the keyboard interrupt code with DEBUG.  Tedious but
not too difficult if you're rather fluent with assembly.
It helps to boot from a floppy disk with no TSR's.
(I've done it once before.)