Subject: Re: [stella] some more optimization tips From: "Andrew Davie" <adavie@xxxxxxxxxxxxxxxxx> Date: Sat, 9 May 1998 21:38:23 +1000 |
Mmmh.. well I've actually started writing my game, now its (ahem) designed. Just thought I'd share the very first stages of the program.. here's an efficient memory clear for you... ; CLEARS ALL VARIABLES, STACK ; INIT STACK POINTER ; ALSO CLEARS TIA REGISTERS ; DOES THIS BY "WRAPPING" THE STACK - UNUSUAL LDX #0 TXS PHA ; BEST WAY TO GET SP=$FF, X=0 TXA CLEAR PHA DEX BNE CLEAR ; 9 BYTES TOTAL FOR CLEARING STACK, MEMORY ; STACK POINTER NOW $FF, A=X==0 Of course, this is untested so here's hoping I won't be red-faced. I would note that Nick Bensema's excellent "How To Draw a Playfield" (thanks, Nick) does it this way... LDX #$FF TXS ; Set stack to beginning. LDA #0 B1 STA 0,X DEX BNE B1 This is fine - a byte longer - but it fails to clear location 0. It really needs an INX or a TAX just before the loop starts - making it 2 bytes longer. His code is, however, much more readable than mine, which is why I like mine better :) Maybe I should stop - am I flooding? A -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/stella.html
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