INES Mapper 087

J87

Company	Konami, Jaleco, Taito
Boards	JF-0x, JF-10 (Jaleco), FC-009 (Taito), MF4034/30xxA (Konami)
PRG ROM capacity	32K
PRG ROM window	n/a
PRG RAM capacity	None
CHR capacity	16k (most games), 32K (JF-09/JF-10 only)
CHR window	8K
Nametable mirroring	Fixed H or V, controlled by solder pads
Bus conflicts	No
IRQ	No
Audio	No
iNES mappers	087, 101

NESCartDB

iNES 087

J87 (Also known as Mapper 87) refers to the first "mapper" created for the Famicom. Despite this, no games with this mapper ever made it overseas to USA NES owners. iNES Mapper 101 is the same board, but for a dump that naïvely reversed the CHR bit-order. CNROM is a later cost-reduced version of this mapper, by cutting down on one logic chip, at the cost of having bus conflicts, and also has the CHR bank order reversed as well. Most games are capped at 16k CHR, however, the JF-09 and JF-10 boards contain an additional trace that allows the design to address 32k. All games with this mapper are emulated as the 32k variant.

The name "J87" was given to this mapper due to its historical significance, and creation by Jaleco. Otherwise, no "canonical" name was given to this mapper. Jaleco would later upgrade this mapper to become iNES Mapper 140.

Banks

• CPU $8000-$FFFF: 16 KB PRG ROM, fixed (if 16 KB PRG ROM used, then this is the same as $C000-$FFFF)
• CPU $C000-$FFFF: 16 KB PRG ROM, fixed
• PPU $0000-$1FFF: 8 KB switchable CHR ROM bank

Registers

Bank Select ($6000-$7FFF)

This will select an 8 KB CHR ROM bank for PPU $0000-$1FFF.

7  bit  0
---- ----
xxxx xxLH
       ||
       |+- High CHR bit
       +-- Low CHR bit