A retrocomputing project has recreated the 1983 Apple Lisa's hardware inside a field-programmable gate array (FPGA), enabling detailed analysis and experimentation with the original machine's architecture. The LisaFPGA project targets a Xilinx Ultrascale+ FPGA and reproduces the Lisa's 68000-based CPU, its NuBus and SCSI interfaces, and the original mouse and GUI behavior.
Overview
The Apple Lisa, released in 1983, was one of the first commercial personal computers with a graphical user interface and a mouse. Its 68000 CPU, NuBus expansion slots, and SCSI storage interface were innovative for their time but also made the machine complex and expensive. The LisaFPGA project aims to recreate this hardware faithfully in an FPGA, allowing users to run original Lisa software and study the system's design without needing a working vintage machine.
What it does
The FPGA implementation replicates the Lisa's core components:
- 68000 CPU – The original Motorola 68000 processor is emulated at the logic level.
- NuBus – The expansion bus used for peripherals and memory is recreated.
- SCSI interface – The storage controller is implemented to support original hard drives or disk images.
- Mouse and GUI – The iconic input device and graphical interface are reproduced, including the original pixel-level rendering.
The project is not a software emulator but a hardware-level recreation using an FPGA, meaning the logic gates and signal timings mimic the original chips. This allows for cycle-accurate behavior and the ability to probe internal signals for debugging or analysis.
Tradeoffs
FPGA recreations offer several advantages over software emulation:
- Accuracy – Logic-level replication can match the original's timing and behavior more closely than a high-level emulator.
- Experimentation – Users can modify the hardware design, add new peripherals, or test modifications without risking a vintage machine.
- Preservation – The design can be archived and reproduced as long as the FPGA hardware is available.
However, there are limitations:
- Cost – The required Xilinx Ultrascale+ FPGA board is expensive and not a consumer item.
- Complexity – Setting up the project requires knowledge of FPGA toolchains and hardware design.
- Completeness – The project may not support every original peripheral or software title, and some edge cases may differ from the original hardware.
When to use it
The LisaFPGA project is primarily useful for:
- Retrocomputing enthusiasts who want to run original Lisa software without maintaining a vintage machine.
- Hardware researchers studying the Lisa's