Date: Mon, 27 Feb 1995 11:59:15 EST
From: THE MASKED PROGRAMMER <badcoe AT bsa DOT bristol DOT ac DOT uk>
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: One More Confused Interrupt Question

From:	BSA::BADCOE       "THE MASKED PROGRAMMER" 23-FEB-1995 11:36:34.29
To:	MX%"dgjpp AT sun DOT soe DOT clarkson DOT edu"
CC:	BADCOE
Subj:	One More Confused Interrupt Question


Hi,
	I want, ultimately, to reprogram the dos clock-tick to a suitable
rate to use for synchronising my VGA redraws with the retrace.  (Note, this
might not be a good thing to do, I might end up using some other timer ?
But ... )

	To do this I have to master interrupts, so some (naive) questions:

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

(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.

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

	Badders