Pi1541

This is picture of a Raspberry PI, with a Pi1541 hat on it, connected to a 8-bit Commodore 64 from 1984 (off camera). The Raspberry Pi 3 at the bottom is more than a thousand times more powerful than the Commodore 64 it is connected to.

The early Commodore computers, PET, VIC-20 and the 64 all shared a rather dumb floppy drive interface. To get round the limitations of the early PET and VIC systems Commodore put the DOS only on the disk drives and kept the actual computers simple. This design was carried forward to the 64, which eventually became a serious annoyance owing to the famously poor reliability and performance of the Commodore floppy drives.

The interesting thing is that the Commodore floppy drives contain their own 6502 CPU, RAM and ROM, which could be carefully reprogrammed to speed them up (fast loaders) but it also means that they can be emulated by the Raspberry Pi, and then with the benefit of the hat connected to a real computer.

Using a Raspberry PI and some voltage shifters it's possible to emulate in software the whole inner workings of the floppy drive and then copy the files off a real disk onto a virtual one, and then you can use them either with the virtual floppy drive or in an emulator of the whole Commodore 64 and floppy drive on a modern PC.

The upshot of all this is that I've been copying my original 5.25" floppy disks to an SD card using the Pi1541 so I can be sure I'll always have copies of my old BASIC programs, and any games I had back in the last century before the disk, the drive or my computer goes bad (they don't last all that well).