🚀 go-pugleaf

>I beleive its not a good idea to use the vertical retrace interrupt because
> according to "Programmers Guide to PC and PS2 video systems" hardware
>interrupts on IRQ2 cannot be distinguished from Vertical interrupts. I'm not
>that cluey on the subject but if its in the book ??? Apparently bus versoins
>of the Microsoft mouse cause this problem, and possibly other hardware that
>use IRQ2. If you are still keen on using it, The book shows you how.
>Themie

I found the book I was muttering about - I had all the details wrong. It is
put out by McGraw Hill, and is titled "EGA/VGA A programmer's Reference Guide."
The author is Kliewer. It *is* filled with typographical errors, so I still
don't suggest anyone buy it. But on pg. 195-199 there is a lot of detail on
writing code to accept and recognise the Vert. Interrupt. Different hardware,
the book warns, does it differently. There are also (ASM) coding examples,
and a wealth of info about EGA and VGA register programming.

I've never done it. To be honest, the book convinced me that I didn't need
to do it. Not with the amount of work required to cover various kinds of
hardware out there. Once enabled, you get interrupts at 0a, and you
have to ask the display board if it caused the interrupt or not. You have
to do special things to clear the interrupt, and the special things seem
to depend on the board.

Good luck. But what is wrong with just painting your images as you generate
them, possibly waiting for the beginning of VR by polling, if you really
need to?
--
He is a slave to a sign who uses or worships a significant thing without
knowing what it signifies.			-Augustine
smayo@wang.com