Date: Mon, 27 Feb 95 11:44:31 -0500
From: dj AT stealth DOT ctron DOT com (DJ Delorie)
To: badcoe AT bsa DOT bris DOT ac DOT uk
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: One More Confused Interrupt Question


> (i) What is the difference between a Real Mode interrupt and a Protected Mode
>     interrupt.

What mode the CPU happens to be in when the interrupt happens.  This
determines the method needed to get the interrupt to your application.

> (ii) Why, when I use the example from the documentation (which hooks the clock
>      tick and uses it to increment a volatile int) does the int seem to
>      increase (a) erratically and (b) far more slowly that 18.3 times per
>      second.

That example does not hook the real-mode half; if a tic happens when
you're doing the printf (and thus in real mode), you miss it.

> (iii) If I use the provided _go32_* functions do they put a lot of overhead
>       into the interrupt servicing ?

If you handle the interrupt and return, no.  If you chain, some, but
this is due to the chaining itself and not the go32 overhead.