NES 2.0 Mapper 285
NES 2.0 Mapper 285 is used for the A65AS and JY-066 multicarts. The UNIF board name for both incompatible variants is BMC-A65AS. A second UNIF board name, BMC-GF-401CD refers to submapper 1. A later-discovered Russian bootleg cartridge of Highway Star (Русские Гонки) is assigned to mapper 285 submapper 1 as well, as it uses UNROM-banking while changing mirroring via latch bit 3.
- CPU $8000-$BFFF: In 16 KiB mode: 16 KiB switchable inner bank, 128 KiB switchable outer bank
- CPU $C000-$FFFF: In 16 KiB mode: 16 KiB fixed inner bank 7, 128 KiB switchable outer bank
- CPU $8000-$FFFF: In 32 KiB mode: 32 KiB switchable bank
- PPU $0000-$1FFF: 8 KiB unbanked CHR-RAM
Bit 7654 3210
---------
SPMO OBBB
|||| |+++- Select 16 KiB inner PRG-ROM bank at CPU $8000-$BFFF in 16 KiB mode (bit 6=0)
|||| |++-- Select 32 KiB PRG-ROM bank at CPU $8000-$FFFF in 32 KiB mode (bit 6=1)
|||+-+---- Select 128 KiB outer PRG-ROM bank at CPU $8000-$FFFF in 16 KiB mode (bit 6=0)
||+------- Select nametable mirroring
|| 0: Vertical (bit 7=0)/Single-screen, page 0 (bit 7=1)
|| 1: Horizontal (bit 7=0)/Single-screen, page 1 (bit 7=1)
|+-------- Select PRG banking mode
| 0: 16 KiB
| 1: 32 KiB
+--------- Select nametable mirroring type
0: Horizontal/vertical
1: Single-screen
Bit 7654 3210
---------
SPMO HBBB
|||| |+++- Select 16 KiB inner PRG-ROM bank at CPU $8000-$BFFF in 16 KiB mode (bit 6=0)
|||| |++-- Select 32 KiB PRG-ROM bank at CPU $8000-$FFFF in 32 KiB mode (bit 6=1)
|||| +---- Select nametable mirroring if bit 7=0
|||| 0: Vertical
|||| 1: Horizontal
||++------ Select 128 KiB outer PRG-ROM bank at CPU $8000-$FFFF in 16 KiB mode (bit 6=0)
||+------- Select nametable mirroring if bit 7=1
|| 0: Single-screen, page 0
|| 1: Single-screen, page 1
|+-------- Select PRG banking mode
| 0: 16 KiB
| 1: 32 KiB
+--------- Select nametable mirroring type
0: Horizontal/vertical (selected via bit 3)
1: Single-screen (selected via bit 5)