NES 2.0 Mapper 448

NES 2.0 Mapper 448 denotes the VRC4-based 830768C multicart circuit board used by a Super 6-in-1 multicart. The VRC4 clone's A0/A1 inputs are connected to CPU A2/A3, and its PRG-RAM chip-enable signal drives an outer bank register. The VRC4 is otherwise mainly used for its IRQ and mirroring selection functionalities; discrete circuits implement UNROM/UOROM/AOROM-like PRG banking with 8 KiB of unbanked CHR-RAM.

Outer Bank Register ($6000-$7FFF, write)

A~[0110 .... .... BUPP]
                  |+++- PRG A19..A17
                  |+--- Fixed bank when B=0
                  |      0: 7 (UNROM)
                  |      1: 15 (UOROM)
                  +---- PRG mode
                         0: UNROM/UOROM
                         1: AOROM

In UNROM/UOROM mode, the VRC4's PRG register at $8000 selects the 16 KiB PRG bank at $8000-$BFFF, and mirroring depends on the VRC4's normal mirroring register. In AOROM mode, the VRC4's PRG bank and mirroring is ignored, and the entire $8000-$FFFF address range functions like INES Mapper 007 with respect to PRG banking and single-screen mirroring, subject only to PRG A19 and A18 set via the outer bank register.