SSF2 Mapper vs WRAM vs SRAM?

Discussion in 'Discussion & Q&A' started by FireRat, Nov 4, 2016.

  1. FireRat

    FireRat "The grand imitator..." Member

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    Hello.
    I have been interested on experimenting with the SSF2, however, I don't think Bobesh8's thread is too reliable for a number of reasons, so I tried to find any other possible documents, and I have been experimenting with this: https://segaretro.org/SSFII_Genesis_Technical_Information_(2000-07-26)

    Now, I know there's some tricky details in overall system's setup that aren't too reliable to test from any emulator. Some emulators do support the mapper, but still don't support larger ROMs!
    So I have one concern, and is about the register at $A130F1. First of all, that there's 1% of probability it works internally from console's side. The document says that by setting bit 0, the area from $200000 to $3FFFFF will bank switch to "RAM".

    > Does it mean the "Work RAM"? or the typical RAM everyone is used to work with, from $FF0000 - $FFFFFF. If so, how does it fill the remaining space? by mirroring the RAM multiple times?
    > Does it mean the "Save RAM? or SRAM. Setting this to 1 to enable SRAM merely mean that it's just the same method for normal ROMs even (and therefore I'm 80% sure that this is the correct behavior).

    If the latter happen to be correct, what emulators are known to support every port properly and what not?
     
  2. Dandaman955

    Dandaman955 She wakes up with the sun... Member

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    Probably completely misinterpreting the question, but it's probably talking about SRAM; That's the SRAM mapping switch.
     
    Last edited: Nov 4, 2016
  3. Natsumi

    Natsumi Markey's Member

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    You set bit 0 of $A130F1 to enable SRAM and clear bit 0 to disable SRAM. There's also other protection bit that was never used anywhere. It would essentially enable read only. Now, what is considered SRAM actually depends on the implementation, seems like the standard was to mirror the upper 2MB as SRAM, but it is not guaranteed to be the case.