65C02 Plus ATmega4809 Equals Colin Maykish's VR65C02, a Functional 2-Chip PC

Colin Maykish has developed a two-chip, eight-bit computer called the VR65C02, which combines a 65C02 microprocessor with an ATmega4809 AVR microcontroller. The 65C02 serves as the CPU, executing 6502-native code, while the ATmega4809 emulates the RAM, ROM, and I/O devices necessary for the system's operation. The ATmega4809, utilized in the updated Arduino Nano Every, features 6 kilobytes of RAM and 48 kilobytes of Flash memory. The process of programming the VR65C02 involves converting 65C02 code into a binary file, which is then transformed into a C-header file for use in an Arduino sketch. The AVR's emulation capabilities allow it to simulate the bus control signals and manage the RAM and ROM as large arrays. The system operates at an effective clock speed of 183 kHz, which is a limitation due to the emulation process. Future enhancements could include using additional GPIOs for chip selection to facilitate data transfer to external RAM, potentially increasing the clock speed. The project resources, including the build script and Arduino sketch, are available on GitHub, along with detailed documentation on the interaction between the AVR and the 65C02.

- Colin Maykish created the VR65C02, a two-chip computer using a 65C02 microprocessor and an ATmega4809 AVR microcontroller.

- The ATmega4809 emulates RAM, ROM, and I/O devices, allowing the 65C02 to run 6502-native code.

- The effective clock speed of the VR65C02 is 183 kHz, limited by the emulation process.

- Future improvements may include external RAM integration to enhance performance.

- Project resources and documentation are available on GitHub.