Pi1541 Is a Cycle-Exact Commodore 1541 Floppy Drive Emulator That You Can Run on Your Raspberry Pi

The Commodore 1541 floppy disk drive had one of the earliest implementations of hardware copy protection in the home computer industry. The drive itself was technically a computer, and had its own CPU, ROM, and RAM, which afforded software developers the opportunity to protect their disks by only allowing them to load under defined conditions. Those companies no longer produce the ancient 5–1/4" floppy disks — or they’re simply defunct now — which poses a unique challenge for retrocomputing enthusiasts who want to run the software on their Commodore 64s.

To skirt the copy protection, as well as provide compatibility for most fast loaders, Steve White has created Pi1541. He’s made the software free, so anyone can run it on their Raspberry Pi 3, and it works by emulating the computer inside of the Commodore 1541. Disk images are stored on the Raspberry Pi’s SD card, and are run through the cycle-exact emulator that sends the data to the Commodore 64 through a custom serial cable.

The Pi1541 emulator being cycle-exact is the key to its ability to handle the disk copy protection, which relies on the timing of the 6502 and 6522 microprocessors used in the Commodore 1541. Once it’s setup, it can successfully fool a Commodore 64 into thinking it’s communicating with a real 1541, allowing you to run the software. It can even run fast loaders, since the emulator is able to actually execute the code on the simulated 6502 microprocessor. If you’ve got a Commodore 64, this is the disk drive solution you’ve been hoping for!