INES Mapper 012

iNES Mapper 012 denotes ...

• the 哥德 (Gouder) SL-5020B circuit board (submapper 0);
• ROM images that have been extracted from disk images for the Front Fareast Magic Card 4M RAM cartridge (submapper 1).

Even as FFE 4M was assigned earlier (as "FFE F6xxx") than SL-5020B, the latter was emulated earlier and so is assigned submapper 0.

SL-5020B (submapper 0)

Submapper 0's circuit board mounts a chip-on-board variant of the same Huang-1 ASIC as mappers 14, 116 and 238 plus GAL16V8 programmable logic. It is used for two games:

• Rex Soft's Dragon Ball Z 5 cartrige;
• Version 7.5 of the homebrew hack Ultimate Mortal Kombat III.

The Huang-1 ASIC functions exclusively as an MMC3A clone on this PCB; MMC3A-specific IRQ behavior is necessary for running Dragon Ball Z 5. The GAL16V8 provides an outer CHR bank register at $4132 to support 512 KiB of CHR-ROM:

Mask: $E100

D~7654 3210 (write)
  ---------
  ...B ...A
     |    +- CHR A18 when PPU A12=0
     +------ CHR A18 when PPU A12=1

Because this register is implemented outside the ASIC, it is not affected by MMC3 $8000 bit 7, and writes take effect immediately. FCEUX instead emulates it as a temporary latch register that takes effect on the next write to an MMC3 CHR bank register. The homebrew hack Ultimate Mortal Kombat III relies on FCEUX' behavior and would therefore not work on the original PCB.

Dragon Ball Z 5 reads the same address to select between Chinese and English text.

Mask: $E100

D~7654 3210 (read)
  ---------
  .... ...A
          +- Language-determining bit value

It was previously thought that the value of this bit reflects a jumper or solder pad. Pictures of the circuit board however show no sign of either. Either such a solder pad is hidden underneath the GAL16V8, or the GAL16V8 has the value hard-wired (to Chinese text in all known copies).

See also: Forum thread about adding parts to an MMC3A board to make this mapper

• 

  PCB front

• 

  PCB back

Front Fareast Magic Card 4M (submapper 1)

Submapper 1 denotes ROM images that have been extracted from disk images for the Front Fareast Magic Card 4M RAM cartridge. It represents games whose Doctor Header file denotes a Magic Card 4M disk (byte $0 bit 7 set, bits 4 or 5 set, byte $7=$00). Refer to the Super Magic Card article for details on bankswitching. The Super Magic Card's registers are initialized to:

; Play mode, WRAM bank 0, 1 KiB CHR mode disabled
$4500 = $42 

; PRG memory write-protected, two-screen mirroring
$42FF = $20 | (verticalMirroring? 0x00: 0x10)

; 4M banking mode enabled
$43FC = $00

; Initial PRG register content
$4504 = Number of 8 KiB PRG banks -4
$4505 = Number of 8 KiB PRG banks -3
$4506 = Number of 8 KiB PRG banks -2
$4507 = Number of 8 KiB PRG banks -1

The iNES header may specify a 512-byte trainer (corresponding to Doctor Header file's byte $0 bit 6 being set), which must be loaded to $7000-$71FF, be writable, and (on a hard reset) initialized by JSRing to $7003 before JMPing to the game's reset vector.

Battery-saving of WRAM content is not supported by any Magic Card model. Hard-resetting a game while restoring previously-saved WRAM content in emulators interferes with the correct operation of the trainer's program.

Because the Magic Card 4M only had 32 KiB of CHR-RAM, CHR data is loaded into PRG address space at offset $40000, i.e. the second half of its 512 KiB of PRG memory, so that the trainer program can copy portions of it to 32 KiB CHR-RAM as needed. The iNES header specifies it as CHR-ROM nonetheless so that the initial PRG registers can be correctly initialized to point to the game's reset vector.