NES 2.0 Mapper 518 is used for several games and educational computer cartridges from Subor:
Its UNIF board name is UNL-DANCE2000. It banks PRG-ROM in 16 or 32 KiB amounts, has 8 KiB WRAM, and 2x4 KiB of CHR-RAM that can be bankswitched according to the current nametable offset during rendering.
小霸王 Subor V was sold both as the built-in BIOS of the Subor SB-97 educational computer, and as a stand-alone cartridge; both versions have identical ROM content. The stand-alone cartridge is a plug-through cartridge to which an expansion cartridge can be connected. In its built-in SB-97 configuration, is additionally has access to a 3.5" floppy disk drive and controller, as well as 128 KiB of secondary PRG-RAM.
Bit 7654 3210 REPP PPPP ||++-++++- Select 16 or 32 KiB PRG bank at CPU $8000 |+-------- 0: Bank comes from main cartridge | 1: Bank comes from expansion cartridge +--------- 0: Bank comes from ROM (main or expansion cartridge) 1: Bank comes from 128 KiB secondary PRG-RAM (SB-97 only)
In 16 KiB PRG banking mode, $C000-$FFFF always comes from main cartridge ROM bank #0. ROM images of expansion cartridges contain the main cartridge data in their first 1 MiB, followed by the expansion cartridge's 1 MiB of data. This means that the 'E' bit needs no special treatment in emulators, as it merely maps to PRG A20 of the combined 2 MiB address space.
Bit 7654 3210 .... .SBM ||+- Select nametable mirroring || 0: Vertical || 1: Horizontal |+-- Select CHR-RAM banking mode (during PPU read accesses only) | 0: 8 KiB CHR-RAM at PPU $0000-$1FFF | 1: 4 KiB CHR-RAM at PPU $0000-$0FFF automatically switched, 4 KiB CHR-RAM at PPU $1000-$1FFF fixed to second half of CHR-RAM +--- Select PRG-ROM bank size 0: 16 KiB PRG-ROM bank at CPU $8000-$BFFF, $C000-$FFFF fixed to first PRG-ROM bank 1: 32 KiB PRG-ROM bank at CPU $8000-$FFFF