Re: [stella] Repository

Subject: Re: [stella] Repository
From: Nick S Bensema <nickb@xxxxxxxxxxxx>
Date: Mon, 23 Feb 1998 13:37:37 -0700 (MST)
> At 06.11 23/02/98 -0800, Greg Troutman wrote:
> >Nick S Bensema wrote:
> >> 
> >> > 1- learn the basic concepts from the programmer's guide. And I mean
> >> > "basic": don't waste time on VDEL, for example! What's the use of VDEL,
> >> > anyway? ;-)
> >> 
> >> It's my understanding that when VDEL is enabled, a player's graphics don't
> >> change immediately when its data register changes; it waits until the
> >> next write to player data before it makes the change.  This was intended
> >> to allow single-scanline positioning in double-scanline kernels, but
> >> its most common use is in six-digit scoring routines.
> I was almost joking, VDEL is very important, thought maybe it's not a clear
> issue at all - and I did't use it in Oystron.
> Exercise: take a simple kernel, let's say Adventure, remove the VDEL (just
> change the STA VDELPx to two NOPs with PCAE) and see what happens.

Harder exercise: modify Adventure or Combat to a single-scanline kernel.
Whether this yields more detailed shapes or ahalf-height screen, you
decide.  With Adventure, you might need to either use bankswitching or
crowd out the Warren Robinett message.

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