Subject: Re: [stella] Starmaster disassembled From: "Thomas Jentzsch" <tjentzsch@xxxxxx> Date: Thu, 2 Aug 2001 11:48:09 +0200 |
Glenn Saunders wrote: > >> > This was not the first game for the 2600 Alan wrote, so maybe somebody else > started or was involved into the project. Yes, that could be, or he reused old code from other of his games. I have to look at Checkers, there could be a similar encoding code. > << > Al invented playfield bitmaps in Surround. That's no easy feat. Take a > look at Surround and see if there are any LSRs. I find it hard to believe > that he didn't know the entire 6502 instruction set by the time Starmaster > was coded I had a look at disassembled Surround code, look what i found (there are several similar parts): LDA $F6 ;3 AND #$F0 ;2 LSR A ;2 LSR A ;2 LSR A ;2 LSR A ;2 TAY ;2 LDA LF78F,Y ;4 CLC ;2 ADC LF799,X ;4 He is masking out the lower 4 bits with AND #$F0 and(!) later he is clearing the carry. It's unneccessary to do both, he should have chosen CLC, because it's uses only 1 byte. To me it looks, like he sometimes(?) had some problems with shifting to the right :) > Starmaster is 4K or 8K? I could understand having some "slop" in an 8K game > if there was plenty of room to spare and if the programmer was trying to > crank out product. David Crane was especially prolific. Al Miller less so, > but also no slouch. It's only 4K, with some size optimizations like overlapping tables etc. He definitely was short of ROM space. Have fun! Thomas _______________________________________________________ Thomas Jentzsch | *** Every bit is sacred ! *** tjentzsch at web dot de | _______________________________________________________________________ 1.000.000 DM gewinnen - kostenlos tippen - http://millionenklick.web.de IhrName@xxxxxx, 8MB Speicher, Verschluesselung - http://freemail.web.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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