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SubjectRe: NES rom FF opcode Reply to this message
Posted byKMDK
Posted on07/06/08 09:30 AM



> > Hi,
> > I've built a disassembler for the NES roms to test the 6502 cpu of my nes
> > emulator. However the disassembler showed many FF opcodes (mostly chained in
> > long groups of FF op's). I used other NES disassemblers to compare the output
> so
> > to rule out errors and I also looked at the binary data directly. So I would
> > like to know why there are so many FF opcodes in Nes roms (e.g. zelda, SMB2,
> > Ninja Gaiden)?
> >
> > Thanks
> >
>
> It's not an opcode -- it's just meaningless data you're looking at. Long runs of
> 0xFF usually mean that part of the ROM has not been programmed with anything.
>
>
> ----
> Bart
>

So why do they have these "gaps" in the program? Why isn't the whole program (game) burnt on the ROM without them (i.e as one big chunk)?



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Entire Thread
Subject  Posted byPosted On
*NES rom FF opcode  KMDK07/05/08 08:07 AM
.*Re: NES rom FF opcode  Bart T.07/05/08 02:07 PM
...Re: NES rom FF opcode  KMDK07/06/08 09:30 AM
...*Re: NES rom FF opcode  Bart T.07/06/08 03:37 PM
....*Re: NES rom FF opcode  smf07/31/08 05:54 PM