Subject: Re: [stella] Qb: BETA 1.0 From: Thomas Jentzsch <tjentzsch@xxxxxx> Date: Sat, 3 Mar 2001 15:04:43 +0100 |
Andrew Davie wrote: > ... sneaky. I've not used this yet, as I've only JUST understood it. Got > the flu :( Get well soon! >> 9. exchange x and y here: >> ZapPF sta playfield,y > I'm not sure what you're suggesting, and why, on the above. Due to absolute > addressing?? Yes, the 6502 has no opcode for sta ZP,y, so the compiler uses sta ABS,y instead, which costs one byte. I'm always trying to use x for zero-page RAM access and y for reading ROM tables. Look at the DASM listing file (just search for 00 in the 3rd opcode column) and you might spot other places (i.E. initscore) where you could optimize. So, if you replace: sta playfield,y ; = 3 bytes with: sta playfield,x ; = 2 bytes you will gain 2 bytes at ZapPF. Have fun! Thomas _______________________________________________________ Thomas Jentzsch | *** Every bit is sacred ! *** tjentzsch at web dot de | - Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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