CPU

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The NES CPU core is based on the 6502 processor and runs at approximately 1.79 MHz (1.66 MHz in a PAL NES). It is made by Ricoh and lacks the MOS6502's decimal mode. In the NTSC NES, the RP2A03 chip contains the CPU and APU; in the PAL NES, the CPU and APU are contained within the RP2A07 chip.


  • Instruction list
  • Memory map
  • Pinout
  • Powerup state
  • status flag behavior


Note

  • The CPU's clock is obtained by dividing a 21.477272 MHz clock source by 12 (26.601712 MHz divided by 16 for PAL).
  • Kevtris has confirmed that all illegal 6502 opcodes execute identically on the 2A03/2A07. He has even went as far as to integrate them into the CopyNES BIOS.
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