mapper 97?

Discuss emulation of the Nintendo Entertainment System and Famicom.

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Zepper
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mapper 97?

Post by Zepper »

The wiki brings the following info:

Code: Select all

   $8000-BFFF:  [M..P PPPP]
     P = PRG Reg  (16k @ $C000)
     M = Mirroring:
        %0 = Horz (PPU A11)
        %1 = Vert (PPU A10)
Disch' mapper 97 document brings a bit different:

Code: Select all

  $8000-FFFF:  [MM.. PPPP]
    P = PRG Reg  (16k @ $C000)
    M = Mirroring:
       %00 = 1ScA
       %01 = Horz
       %10 = Vert
       %11 = 1ScB
What is the correct information?
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Quietust
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Re: mapper 97?

Post by Quietust »

In practice, it's actually a bit of both - the only game which used it had 256KB of PRG ROM (which only requires 4 PRG bank bits), and the way the mapper chip is wired on that board means that only H/V mirroring is available via D7, but if you emulate it according to Disch's document it'll still work (because the game always writes either $8x or $4x).

More details can be found here.
Quietust, QMT Productions
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aquasnake
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Re: mapper 97?

Post by aquasnake »

Merge to maximize expansion:)

Code: Select all

 $8000-FFFF:  [MM.P PPPP]
    P = PRG Reg  (16k @ $C000)
    M = Mirroring:
       %00 = 1ScA
       %01 = Horz
       %10 = Vert
       %11 = 1ScB
mirroring[1:0] = {~(cpu_data_in[7] ^ cpu_data_in[6]), cpu_data_in[6]};
Last edited by aquasnake on Fri May 28, 2021 8:25 pm, edited 1 time in total.
lidnariq
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Re: mapper 97?

Post by lidnariq »

aquasnake wrote: Fri May 28, 2021 8:07 pm Merge to maximize expansion:)
Absolutely no valid reason to do that. There's only one game that's mapper 97, and Disch's old documentation is an arbitrary superset.
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aquasnake
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Re: mapper 97?

Post by aquasnake »

lidnariq wrote: Fri May 28, 2021 8:11 pm
aquasnake wrote: Fri May 28, 2021 8:07 pm Merge to maximize expansion:)
Absolutely no valid reason to do that. There's only one game that's mapper 97, and Disch's old documentation is an arbitrary superset.
yes, Ockham's principle
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