Mail Archives: djgpp/1997/02/26/19:07:02
Robert Hentosh writes:
>wondering why some games can run under a DOS shell in Win95 and others
>need to reboot the machine into DOS mode. Does just changing the
>Timer interrupt enough to cause Windows to goes nuts in some
Reprogramming the timer is fine, as long as you do it once and then
don't alter it. win95 will allow you to accelerate the timer interrupt,
but it doesn't notice the first time you alter it: to be sure it has
been accelerated, I have to do a little loop and write the same values
to the PIT registers five or six times... If you try to alter the timer
speed on the fly, from inside your handler, win95 gets upset: it works,
but the changes are delayed by two or three interrupts, and it moans
about how your program ought to be run in DOS mode.
Apart from that, keyboard and soundcard interrupts seem to work the same
as under DOS. The only thing to be aware of is that win95 will preempt
your program at odd moments, which can cause timer interrupts to be
delayed (under win95, 16 bit driver code isn't interrupted by 32 bit
interrupts, no matter how long the driver is taking to do it's stuff)
and sometimes makes retrace polling loops miss the fact that a retrace
just occured. This tends to make everything far more jerky than under
DOS, but there isn't a lot you can do about it...
>instances? What things should I avoid? Extended Memory? Expanded
>Memory?
Why would you want to use these? Horrible things :-) Use djgpp, and all
your memory is a flat 32 bit address space allocated with DPMI
functions...
/*
* Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
* Beauty is a French phonetic corruption of a short cloth neck ornament.
*/
- Raw text -