Re: [stella] zero page 6-digit routine

Subject: Re: [stella] zero page 6-digit routine
From: Erik Mooney <emooney@xxxxxxxxxxxxxxxx>
Date: Thu, 26 Mar 1998 15:18:19 -0500 (EST)
> 57 bytes out of 128? :)  I've never written a full game
> for the A2600, but I'm sure that some games could get
> by with the remaining 71... a few bytes could be saved
> by saving the stack pointer externally to the routine,
> I think...  and normally 12 bytes are taken up by the
> zero page pointers - that's integrated into the self
> modifying code, so we're left with "only" 45 bytes
> above a regular 6 digit display.
> 
> Maybe some of the extra cycles could support some extra
> jumps back into and out of ROM, for the non-selfmod
> code, so we'd save RAM space, and still have a net gain
> in cycles free?  I'll have to try that, and get this
> thing moving left and right :)

That might actually work, though I really doubt you could gain enough
cycles to make it worthwhile.  You had 10 more than the  ROM routine,
right?  JMPing to a different page takes four cycles if I remember
correctly, so if you do one of those each way, you gain a whopping two
cycles at a cost of still around 25 bytes of RAM.

Let's not spend forever reinventing the wheel... there's a reason the
original programmers used the routines they did.  If we could improve on
the wheel, letting it roll left and right (let me know when I carry this
analogy too far :) ) it would be worthwhile, but I can already come up
with plenty of ways to waste RAM :)

It might well be worthwhile as/for a Supercharger-only game, though...
saving those 10 cycles at a cost of zero bytes of RAM might help
something.



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