Re: [stella] Star Fire 2600: Star Background

Subject: Re: [stella] Star Fire 2600: Star Background
From: Thomas Jentzsch <tjentzsch@xxxxxx>
Date: Thu, 1 Aug 2002 15:30:13 +0200
Hi Manuel
> Hm... I'm not too sure about that. Consider that with 2LK precission for
> that, you'd lose every second HMOVE, i.e. all stars would then sit on
> only 3 instead of the current 6 diagonals.


> When I had to make this decission, it looked like I needed the sprite
> index way more often than the line counter. Maybe now the # of accesses
> is shifted towards the line-counter, then swapping might gain something.

With using some more RAM variables, I'm sure the linecounter will be accessed
more often.

> I've to check that. I must know the exact gain/loss of that before
> trying such a major impact on the kernel. It is so fragile and relying
> on single cycles at several points, so that tweaking the tables to work
> again after such a change will most likely cost me several hours.

Why don't you annote the timings in your kernel? That helps me alot, when
I'm playing around with it.

Something like:

LDA (ptr),Y; 5
STA GRP0   ; 3 @12 (@ only for TIA registers)

> As for the crosshair, I certainly won't gain any cycles by doing it with
> skipdraw, instead it'd make the problem only worse. 
> No skipping logic can be quicker then:
> LDA table, line

Sure, but I meant you should use "skipDraw" for the sprites (not for the crosshair).

The crosshair code should only be changed into:

LDA (tablePtr), line

> I normally only start thinking, when 1-2 hours "try & error" don't
> produce the desired result ;-)

I'm not that patient, so I start thinking after a few minutes. ;-)


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