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
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