Re: [stella] Fastest missile/ball draw

Subject: Re: [stella] Fastest missile/ball draw
From: M Zach <zach_in_sac@xxxxxxxxx>
Date: Fri, 25 Feb 2005 15:07:16 -0500
Yeah, there is a faster way. It's a classic trick
using the stack pointer and PHP. The advanced
programming guide linked below explains it well.
Search for "using PHP" in the text file.

http://www.qotile.net/minidig/docs/2600_advanced_prog_guide.txt
 
--- Bob Montgomery <BobM@xxxxxxxxxxx> wrote:

> The fastest way to draw a missile or ball (of
> variable height) that I have come up with is this:
> 
> lda BallHeight
> dcp BallYPosition
> sbc BallHeight
> sta ENABL		;+14
> 
> Is there a faster way?
> 
> You can shave a cycle if you restrict your
> BallHeight to intervals of 4:
> 
> lda BallHeight
> dcp BallYPosition
> sbc #0
> sta ENABL		;+13
> 
> Where BallHeight = 0, 4, 8, etc.
> Similar for other BallHeight values.
> 
> And you can shave another cycle by replacing
> BallHeight by #BALLHEIGHT - but is there a faster
> way for the general case?
> 
> Thanks,
> 
> -bob
> 
> PS I've been waiting to subscribe to this list for
> about 4 months; this is my first post!
> 
> Archives (includes files) at
> http://www.biglist.com/lists/stella/archives/
> Unsub & more at http://stella.biglist.com
> 
> 



		
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