NES 2.0 Mapper 444

Front view

NES 2.0 Mapper 444 denotes the NC7000M multicart circuit board. Its UNIF board name is BMC-BS-110, which is the name of a different PCB whose name was mixed-up.

The top-right solder pads are relevant for bankswitching and are denoted by Submapper bits. A clear bit represents the upper pad connection:

• Submapper bit 0 (top-rightmost pad): CHR-ROM A17 connected to $6000.0 (clear) or to the MMC3 CHR A17 output (set). Selects whether the MMC3 can address 128 or 256 KiB of CHR data.
• Submapper bit 1 (the top-second-rightmost pad): CHR-ROM A18 connected to $6000.1 (clear) or to $6000.4 (set). Since PRG A18 is also determined by $6000.1, it thus selects whether CHR A18 can be determined separately or not.

Known cartridges:

• 7000-in-1 (CA-004): both bits set (submapper 3)
• Super 8000-in-1: both bits clear (submapper 0)

Outer Bank and Mode Register ($6000-$7FFF, write)

Mask: $E000

A~FEDC BA98 7654 3210
  -------------------
  011. .... ...C MMBA
               | ||++- PRG A18..17
               | |||+- CHR A17 if submapper bit 0 clear
               | ||+-- CHR A18 if submapper bit 1 clear
               | ++--- Select PRG-ROM mode
               |        0: MMC3 mode
               |        1: NROM-256 mode (PRG A13..14=CPU A13..14, PRG A15..16=MMC3 A15..16)
               |        2: Read solder pads' value in D0/D1 (leftmost pads in picture)
               |        3: NROM-128 mode (PRG A13=CPU A13, PRG A14..16=MMC3 A14..16)
               +------ CHR A18 if submapper bit 1 set

• WRAM must be enabled in $A001.7 before writing to this register.
• The inner PRG bank is restricted to 128 KiB.
• NROM mode forces MMC3's CPU A13 and A14 inputs to GND to make MMC3 bank register 6 apply to the entire CPU $8000-$FFFF range.

MMC3-compatible registers

Mask: $E001

See MMC3.