The picoZ80: A Modern Upgrade for Legacy Z80 Systems

The picoZ80 is an innovative solution for upgrading legacy Z80-based computers by replacing the traditional Z80 CPU with a more powerful and versatile system. This custom PCB fits directly into the Z80 DIP-40 socket and leverages an RP2350B microcontroller, which offers dual-core processing at up to 300MHz. This setup not only maintains the original Z80 bus timing but also enhances the system with additional memory, virtual devices, and network capabilities through WiFi and Bluetooth, managed by an ESP32 co-processor.

The board's architecture allows for real-time handling of bus transactions, ensuring cycle-accurate emulation of the Z80. It supports a wide range of functionalities, such as accelerated execution, virtualized memory, and machine-persona emulation. The configuration is managed via a JSON file on an SD card, allowing easy reconfiguration without recompilation.

Demonstrations have shown the picoZ80 running on various Sharp MZ machines, with plans to extend support to other Z80 systems. The board supports features like banked RAM/ROM, floppy disk emulation, and a ROM Filing System, all configurable through the JSON-driven setup. The ESP32 co-processor provides a web-based management interface for configuration and firmware updates.

The hardware design is compact, fitting within the original Z80 socket space, and includes subsystems for the RP2350B processor, Z80 bus interface, ESP32 co-processor, power supply, and USB hub. The RP2350B handles Z80 emulation and other tasks, while the ESP32 manages network connectivity and storage.

The board's design is open-source, with hardware and firmware available for non-commercial use. The project acknowledges contributions from various open-source communities and individuals, ensuring a robust and versatile platform for retro computing enthusiasts.