CDC Floppy Drive

The Control Data Corporation Model 9400 Flexible Disk Drive is an eight-inch floppy drive that supports single sided, single density or double density floppies. However, currently, we believe the Centurion uses single density formatting. It is important to note that there are three different versions of CDC made, 8" floppy drives. The model shown here is the 9400, but we believe that the Centurion was originally built with either the CDC 9404 or CDC 9406 in mind as the floppy cable pinouts do vary. The command cable is shared with the CDC Finch Drive, and up to four drives can be daisy chained and controlled from the same FFC Controller Board.

Connection Interface

The pinout for the FFC command cable and the CDC 9400 Floppy Drive unfortunately do not match, requiring an adapter board or custom cable to be made. Here is a spreadsheet showing the Finch/FFC pinout on the left and the Floppy/FFC pinout on the right. The corresponding pin on the drive itself is shown in parenthesis.

The Control Board

The Floppy drives pictured above are the CDC Model 9400, were purchased from eBay and restored to mostly working order. The schematics for the control board are included in the manual (linked below), however for confirmation, as well as archival purposes, I took a high resolution scan of the control board when I had it off during troubleshooting.

Right click and "Save As..." or "Open Image in New Tab" for full resolution.

The 9404 and 9046 model Floppy Drives can be distinguished by their very different PCBs. Here are the three PCBs compared against each other:

Brochure

This brochure is for the 9400 model Flexible Disk Drive.

View the full brochure here.

Additional Information

The full manual for the Floppy is available on Bitsavers, but has also been uploaded to this Github for archival purposes.

Full Manual