DxROM

The generic designation DxROM refers to cartridge boards made by Nintendo that use the seemingly-identical Namco 108, 109, 118 or 119 mappers. Nintendo did not manufacture the Famicom counterparts. The iNES format assigns Mapper 206 to DxROM.

The following DxROM boards are known to exist:

Board	PRG ROM	CHR ROM	Comments
DEROM	64 KiB	32,64 KiB ROM	Nintendo's clone of Tengen's 800002 and Namco's 3413 and 3414
DE1ROM	128 KiB	64 KiB	Nintendo's clone of Tengen's 800030 and Namco's 3406
DRROM	128 KiB	64 KiB	Nintendo's clone of Tengen's 800004, with four-screen mirroring.

Tengen initially tried to get around Nintendo's publication restrictions by manufacturing all parts of the games themselves. They were eventually prohibited from continuing, but Nintendo only re-released a subset of all the games that Tengen brought to the US.

Namco published a wide number of differently-numbered Famicom counterparts. Some of them have significantly different behavior and have had their own mappers allocated.

Board	PRG ROM	CHR ROM	Comments
3401	32 KiB	32 KiB
3405, 3415	128 KiB	32 KiB
3406, 3416	128 KiB	64 KiB
3407, 3417, 3451	32 KiB	16,32 KiB	PRG A13, A14 connected directly to CPU, no PRG banking available
3413	64 KiB	32 KiB
3414	64 KiB	64 KiB
3425	128 KiB	32 KiB	CHR A15 controls CIRAM A10
3433, 3443	128 KiB	128 KiB	PA12 controls CHR A16
3446	128 KiB	128 KiB	2K banks using regs 2-5
3453	128 KiB	128 KiB	Bit 6 of written value controls CIRAM A10; PA12 controls CHR A16

Otherwise, the Namco 108 family is just a subset of MMC3