NES 2.0 Mapper 437 denotes the NTDEC TH2348 multicart circuit board for eight UNROM games with an additional outer bank register.
A~[0101 .... .... MOOO]
|+++- PRG A19..A17
+---- Nametable mirroring
0: CIRAM A10=PPU A10 (vertical)
1: CIRAM A10=PPU A11 (horizontal)
Categories: Mappers with CHR RAM, Multicart mappers