TDS3000 and 3000B operate the floppy and parallel port through a "super IO" chip as used on computer motherboards of the era. At TDS3000C they removed the super IO and put in a USB controller.
the floppy drive and printer are driven through a Super I/O chip dedicated to those functions. To add USB support in the C revision, the entire IO section of the TDS3000/B scopes were removed and redesigned with completely different component. -- "Chris B", Tektronix Applications, on the Tek Forum, August 21, 2012.