Hi Jules, ImageDisk works with the standard Nec765 based PC controller, preferably an AT or higher on which the data rate can be set. This has all the limitations inherent in many PC implementations. In testing about a dozen machines, I've found three which can read AND write mixed density disks without complaint. The FDCs on Intel mainboards appear to be quite good if you can live with the fact that they couldn't be bothered to provide a Drive-B select on the interface connector. All of this information (and more) appears in ImageDisks online help. Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.parse.com/~ddunfield/museum/index.html