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).

The circuit board has three solder pads with bankswitching-relevant functionality (plus several others):

• S0: Connect MMC3 CHR A17 to CHR-ROM A17 or not
• S1: Connect $6000.0 to CHR-ROM A17 or not
• S2: Connect $6000.4 or $6000.1 to CHR A18

Known cartridges:

• 快打金卡终极挑战 (Kuàidǎ Jīnkǎ Zhōngjí Tiǎozhàn) 3/6-in-1
  • S0: MMC3 CHR A17 connected to CHR-ROM A17
  • S1: $6000.0 connected to CHR-ROM A17
  • S2: $6000.1 connected to CHR-ROM A18
• 14/400/8000/3000000-in-1
  • S0: MMC3 CHR A17 not connected to CHR-ROM A17
  • S1: $6000.0 connected to CHR-ROM A17
  • S2: $6000.1 connected to CHR-ROM A18
• 7000-in-1 (CA-004)
  • S0: MMC3 CHR A17 connected to CHR-ROM A17
  • S1: $6000.0 not connected to CHR-ROM A17
  • S2: $6000.4 connected to CHR-ROM A18

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

Mask: $E000

A~FEDC BA98 7654 3210
  -------------------
  .... .... ...C DSBA
               | ++++- =$08: CPU $8000-$FFFF D0/D1: menu-selecting solder pads
               | |||| !=$08: CPU $8000-$FFFF D0/D1: normal data
               | ||++- PRG A18..17
               | |||+- CHR A17 if solder pad S1=1
               | ||+-- CHR A18 if solder pad S2=1
               | |+--- 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)
               +------ CHR A18 if solder pad S2=0

• 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.

MMC3-compatible registers

Mask: $E001

See MMC3.