RAMBO-1

The Tengen RAMBO-1 is an ASIC mapper, assigned to iNES mapper 64. This mapper is basically Tengen's version of the MMC3, but with some extra features.

Overview

• PRG ROM size: Up to 2 MB (??)
• PRG ROM bank size: 8 KB
• PRG RAM: Unknown
• CHR capacity: Up to 256 KB ROM
• CHR bank size: All 1 KB, or 2 2KB and 4 1KB
• Nametable mirroring: Controlled by mapper
• Subject to bus conflicts: No

Banks

• CPU $8000-$9FFF: 8 KB switchable PRG ROM bank
• CPU $A000-$BFFF: 8 KB switchable PRG ROM bank
• CPU $C000-$DFFF: 8 KB switchable PRG ROM bank
• CPU $E000-$FFFF: 8 KB PRG ROM bank, fixed to the last bank
• PPU -- Three selectable configurations:
  1. 1 KB switchable CHR banks at $0000, $0400, $0800, $0C00, $1000, $1400, $1800, $1C00
  2. 2 KB switchable CHR banks at $0000, $0800; 1 KB switchable CHR banks at $1000, $1400, $1800, $1C00
  3. 2 KB switchable CHR banks at $1000, $1800; 1 KB switchable CHR banks at $0000, $0400, $0800, $0C00

Registers

The RAMBO-1 has 4 pairs of registers at $8000-$9FFF, $A000-$BFFF, $C000-$DFFF, and $E000-$FFFF - even addresses ($8000, $8002, etc.) select the low register and odd addresses ($8001, $8003, etc.) select the high register in each pair.

Bank select ($8000-$9FFE, even)

7  bit  0
---- ----
CPKx xRRR
|||   |||
|||   +++- Specify which bank register to update on next write to Bank Data register
|||        0: Select 2 (K=0) or 1 (K=1) KB CHR bank at PPU $0000 (or $1000);
|||        1: Select 2 (K=0) or 1 (K=1) KB CHR bank at PPU $0800 (or $1800);
|||        2: Select 1 KB CHR bank at PPU $1000-$13FF (or $0000-$03FF);
|||        3: Select 1 KB CHR bank at PPU $1400-$17FF (or $0400-$07FF);
|||        4: Select 1 KB CHR bank at PPU $1800-$1BFF (or $0800-$0BFF);
|||        5: Select 1 KB CHR bank at PPU $1C00-$1FFF (or $0C00-$0FFF);
|||        6: Select 8 KB PRG bank at $8000-$9FFF (or $A000-$BFFF);
|||        7: Select 8 KB PRG bank at $A000-$BFFF (or $C000-$DFFF);
|||        8: If K=1, Select 1 KB CHR bank at PPU $0400 (or $1400);
|||        9: If K=1, Select 1 KB CHR bank at PPU $0C00 (or $1C00);
|||        F: Select 8 KB PRG bank at $C000-$DFFF (or $8000-$9FFF);
||+------- Full 1KB CHR ROM bank mode (0: two 2KB banks at $0000-$0FFF (or $1000-$1FFF),
||                                     1: four 1KB banks at $0000-$0FFF (or $1000-$1FFF))
|+-------- PRG ROM bank configuration (0: $8000-$9FFF uses bank selected with R:6,
|                                         $A000-$BFFF uses bank selected with R:7,
|                                         $C000-$DFFF uses bank selected with R:F;
|                                      1: $8000-$9FFF uses bank selected with R:F,
|                                         $A000-$BFFF uses bank selected with R:6,
|                                         $C000-$DFFF uses bank selected with R:7)
+--------- CHR ROM bank configuration (0: two 2 KB banks (or four 1 KB banks) at $0000-$0FFF,
                                          four 1 KB banks at $1000-$1FFF;
                                       1: two 2 KB banks (or four 1 KB banks) at $1000-$1FFF,
                                          four 1 KB banks at $0000-$0FFF)