Date: Tue, 30 May 1995 13:14:20 +0300 (IDT)
From: Eli Zaretskii <eliz AT is>
To: Joel Hunter <jhunter AT kendaco DOT telebyte DOT com>
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: Manually calling iret functions



On Mon, 29 May 1995, Joel Hunter wrote:

>   I have kind of a strange question.  I'm going to be reprogramming the PIT
> chip to generate a Timer interrupt more than 18.2 times a second.  But so I
> don't screw up the system's clock, I want to still call the original
> timer-handler-routine, just not every time an interrupt is generated.
> _go32_chain_protected_mode_interrupt_vector()  is obviously not the solution
> -- I need to check to see if the time is right, and if it is MANUALLY call
> the old timer function.  What is the best way to do this? (Ignore real-mode
> for now -- I'm only worried about protected-mode.)

Take a look at the timer code on SimTel.  The file is called 
PCTIME12.ZIP, but I don't recall right now what directory it is in.  Try 
/SimTel/msdos/c.  This code compiles with DJGPP and does what you want.  
You can either use it as is or modify it to your specific needs.