VRC1

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

• Disch's Mapper Notes