Date   : Mon, 23 Jan 1995 13:29:47 +0000
From   : lamcw <lamcw@...>
Subject: Re: Elite

Dave Gilbert wrote:


;I have Elite running OK - except for what sounds like the
;same explosion problem you had - have you fixed it yet?

This is only a problem when I compile my code for the PPC 
computer. On a 68k Mac it's fine - no bugs. So the fact it's
okay on one computer and not on another worries me.
I'm going to recompile it again this afternoon, hope the
problem just goes away.

The fact that you get it too is suspicious. Are ALL the other
graphics in ELITE fine? 


;(Revs isn't working - the switching point is scrolling gently
;up the screen - I haven't figured out why yet).

Yep, I had this problem too. The reason is that your VIA
counters aren't precise enough. REVS does not sync to the
vertical sync interrupt - don't ask me why. What it does
is sync it ONCE and then leave the interrupts to tick over
on their on. That's why the interrupt changes scroll up/down
the screen.

I struggled with this for weeks trying to make the interrupts
more precise. I'm only updating the counters every 15 or so
instructions (for speed) and there's the problem.

In the end, I cheated. I detected that REVS was running and
fiddled the counters to give a rock-steady screen. Works
fine now.


Chris Lam.