INES Mapper 122

iNES Mapper 122 denotes the JY043 circuit board, a simpler bootleg variant of Kaiser's KS-7058 circuit board.

Overview

• CPU $8000-$FFFF: 32 KiB unbanked PRG-ROM
• PPU $0000-$0FFF: 4 KiB switchable window into 32 KiB CHR-ROM
• PPU $1000-$1FFF: 4 KiB switchable window into 32 KiB CHR-ROM
• Nametable arrangement: Selected via solder pad

Registers

There are two writable registers in the CPU $8000-$FFFF address range.

Register 1: Responds to even addresses from CPU $8000-$FFFE

D~[.... .CBA] A~[1... .... .... ...0]
         +++- 4 KiB CHR-ROM bank (CHR A14..A12)
              for PPU $0000-$0FFF

Register 2: Responds to odd addresses from CPU $8001-$FFFF

D~[.... .CBA] A~[1... .... .... ...1]
         +++- 4 KiB CHR-ROM bank (CHR A14..A12)
              for PPU $1000-$1FFF

Notes

• iNES Mapper 122 had at one time been used by the DOS-based fwNES emulator to denote Sunsoft-1, now assigned to Mapper 184.
• JY043 had previously been assigned together with KS-7058 and the BBK Keyboard Famiclone's mapper as INES Mapper 171.