When I was working on my selfbuilt 6502 operating system, I had a file system server on the PC, connected to the 6502 via a serial line (RS232). It was using a generic, packet-based protocol on the serial "wire", so I decided to reuse the protocol and the server for an AVR-based implementation of a Commodore disk emulator. The Commodore would talk to the AVR via IEEE488 or the CBM serial IEC protocol, which would behave as a disk drive and use the wire protocol to talk to the PC to server files from there. In the beginning it looked like a good idea. But it took much more time than expected. Read on for the full story.