For fun and an interesting trip down memory lane, Dave Chaney has worked with the code for a web-based PDP-11 emulator - and come up with a solution that runs on an Arduino Mega 2560 or compatible board, in this case our EtherMega. Although the simulation is still a work in progress, the system has access to a single drive (using the microSD card slot on the Ethermega) and some extra SRAM has been used which is fitted to an external shield. The use of external SRAM ICs decreases the overall speed, but solves the problem caused by the MCU's limitation.
As shown in the project above, Dave uses the Freetronics EtherMega:
Quite simply the EtherMega is the fully-loaded Arduino-compatible board on the market today. Apart from being completely Arduino Mega2560-compatible, it includes full Ethernet interface, a microSD card socket, full USB interface, optional Power-over-Ethernet support and still has a circuit prototyping area with extra I2C interface pins. So if your project is breaking the limits, upgrade to the EtherMega today.