NES 2.0 Mapper 344

NES 2.0 Mapper 344 denotes the GN-26 and NC7000M multicart circuit boards. Its UNIF board names are BMC-GN-26 (with incorrect PRG bank order) and BMC-BS-110 (which is the name of a different PCB whose name was mixed-up).

• 快打金卡终极挑战 (Kuàidǎ Jīnkǎ Zhōngjí Tiǎozhàn) 3/6-in-1, GN-26 PCB
• 14/400/8000/3000000-in-1, NC7000M PCB

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

Mask: $E000

A~FEDC BA98 7654 3210
  -------------------
  .... .... .... DSBb
                 ++++- =$04: CHR A17=MMC3 A17 (256 KiB inner CHR)
                 |||| !=$04: CHR A17=b        (128 KiB inner CHR)
                 ||||  =$08: CPU $8000-$FFFF exposes solder pad setting
                 |||| !=$08: CPU $8000-$FFFF exposes PRG-ROM
                 ||++- PRG/CHR A17..A18
                 |+--- Select PRG-ROM mode
                 |      0: MMC3 mode
                 |      1: NROM mode (see below)
                 +---- PRG A14 mode when S=1
                        0: PRG A14=CPU A14          (NROM-256)
                        1: PRG A14=MMC3 reg 6 bit 1 (NROM-128)

• 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 and replaces MMC3's PRG A13 output with CPU A13. This means that MMC3 bank register 6 bits 1-3 provides PRG A14..A16 for the entire CPU $8000-$FFFF range.
• The common dump of 快打金卡终极挑战 (Kuàidǎ Jīnkǎ Zhōngjí Tiǎozhàn) 3/6-in-1 has the 128 KiB PRG-ROM banks mixed-up, correct would be in the order 0, 3, 1, 2. The 128 KiB CHR-ROM banks were in the correct order all along, making the mapper seem more complicated than it actually is.

MMC3-compatible registers

Mask: $E001

See MMC3.