INES Mapper 225

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 Here are Disch's original notes:  
 ========================
 =  Mapper 225          =
 ========================
 
 Example Games:
 --------------------------
 52 Games
 58-in-1
 64-in-1
 
 
 Registers:
 ---------------------------
 
   $5800-5803:  [.... RRRR]  RAM  (readable/writable)
                 (16 bits of RAM -- 4 bits in each of the 4 regs)
   $5804-5FFF:    mirrors $5800-5803
 
   $8000-FFFF:  A~[.HMO PPPP PPCC CCCC]
     H = High bit (acts as bit 7 for PRG and CHR regs)
     M = Mirroring (0=Vert, 1=Horz)
     O = PRG Mode
     P = PRG Reg
     C = CHR Reg
 
 
 CHR Setup:
 ---------------------------
 
                $0000   $0400   $0800   $0C00   $1000   $1400   $1800   $1C00 
              +---------------------------------------------------------------+
 CHR Mode 0:  |                             $8000                             |
              +---------------------------------------------------------------+
 
 
 PRG Setup:
 ---------------------------
 
                $8000   $A000   $C000   $E000  
              +-------------------------------+
 PRG Mode 0:  |            <$8000>            |
              +-------------------------------+
 PRG Mode 1:  |     $8000     |     $8000     |
              +---------------+---------------+

Nestopia does not implement the 4 × 4 bit RAM, and FCEUX ceased to support it between 2.1.5 and 2.2.1

This looks like a duplicate of iNES Mapper 255. It's not clear why Nestopia implemented it twice.

Pictures of the PCB show physical releases both with and without the 74'670 that make up the extra RAM. Carts are slightly buggy without it.

See also