Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!helios!tamunix!briggs
From: briggs@tamunix (Mark Lowe)
Newsgroups: comp.os.msdos.programmer
Subject: Re: changing cpu speed through software
Keywords: cpu speed
Message-ID: <9802@helios.TAMU.EDU>
Date: 3 Nov 90 05:35:04 GMT
References: <1990Nov3.014940.9232@rice.edu>
Sender: usenet@helios.TAMU.EDU
Organization: Texas A&M University
Lines: 20

In article <1990Nov3.014940.9232@rice.edu> adnan@screech.rice.edu (Sarmad Adnan) writes:
>
>I need to write a piece of code that would allow me to 
>change the speed of the cpu (in a dual speed AT, with
>AMI bios) through software. 
>Some of the compaq have a 'MODE speed' command implimented
>in the dos does something similar exist or can be written
>for a computer with AMI bios ?.
>                  Sarmad Adnan (adnan@rice.edu)

I once wrote a short machine language routine for a former roommate's
computer that had two speeds.  He has one of those computers that allows you
to toggle between speeds by hitting CTRL-ALT-HYPHEN or some such keystroke.
I messed around with the system enough to figure out that an unused bit in
I/O port 60 or 61 controlled the speed.  Make sure you disable interrupts
before toggling the bit, though, or you'll hang the machine.

I hope this vague description gives you some clues.

Mark C. Lowe - KB5III