VRC1

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VRC1
Company Konami
Games 6 in NesCartDB
Complexity ASIC
Boards JF-20, JF-22, 4036, 302114A, 350459
Pinout VRC1 pinout
PRG ROM capacity 128K
PRG ROM window 8K
PRG RAM capacity none
PRG RAM window n/a
CHR capacity 128K
CHR window 4K
Nametable mirroring H or V, switchable
Bus conflicts No
IRQ No
Audio No
iNES mappers 075

The Konami VRC1 is an ASIC mapper. The iNES format assigns mapper 75 to VRC1.

The VRC1 was used in several Famicom games released by Konami and Jaleco:

  • Exciting Boxing
  • Ganbare Goemon! Karakuri Douchuu
  • Jajamaru Ninpouchou
  • King Kong 2: Ikari no Megaton Punch
  • Moero!! Junior Basket: Two on Two
  • Tetsuwan Atom


Banks

  • CPU $8000-$9FFF: 8 KiB switchable PRG ROM bank
  • CPU $A000-$BFFF: 8 KiB switchable PRG ROM bank
  • CPU $C000-$DFFF: 8 KiB switchable PRG ROM bank
  • CPU $E000-$FFFF: 8 KiB PRG ROM bank, fixed to the last bank
  • PPU $0000-$0FFF: 4 KiB switchable CHR bank
  • PPU $1000-$1FFF: 4 KiB switchable CHR bank

Registers

PRG Select 0 ($8000-$8FFF)

7  bit  0
---------
.... PPPP
     ||||
     ++++- Select 8 KB PRG ROM at $8000

PRG Select 1 ($A000-$AFFF)

7  bit  0
---------
.... PPPP
     ||||
     ++++- Select 8 KB PRG ROM at $A000


PRG Select 2 ($C000-$CFFF)

7  bit  0
---------
.... PPPP
     ||||
     ++++- Select 8 KB PRG ROM at $C000


Mirroring Control, CHR bits ($9000-$9FFF)

7  bit  0
---------
.... .BAM
      |||
      ||+- Mirroring  (0: Vertical; 1: Horizontal)
      |+-- High Bit of 4 KB CHR bank at PPU $0000
      +--- High Bit of 4 KB CHR bank at PPU $1000

The mirroring bit is ignored if the cartridge is wired for 4-screen VRAM, as is typical for Vs. System games using the VRC1.

CHR Select 0 ($E000-$EFFF)

7  bit  0
---------
.... CCCC
     ||||
     ++++- Low 4 bits of 4 KB CHR bank at PPU $0000

These bits combined with bit 1 of $9000 make a 5-bit CHR selection.


CHR Select 1 ($F000-$FFFF)

7  bit  0
---------
.... CCCC
     ||||
     ++++- Low 4 bits of 4 KB CHR bank at PPU $1000

These bits combined with bit 2 of $9000 make a 5-bit CHR selection.

References