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[ The PC Guide | Systems and Components Reference Guide | Floppy Disk Drives | Floppy Disk Interfacing and Configuration ]

Floppy Disk Controller Speed

The floppy disk controller included in virtually all new PCs will support every type of standard floppy disk. Older controllers, however, would not work with the newer drives. Generally speaking, the limiting factor was the floppy controller's ability to run at a high enough speed. While the floppy interface is in general very slow--far slower than hard disk interfaces, even at the floppy's top speed--there are in fact different "shades" of slow. :^)

The speed required of the controller is directly related to the density of the floppy disk media being used, in particular the bit density per track. Since higher-density floppies record more information in the same space, they require faster data transfer to the drive, to ensure that the data arrives "on time" to be recorded. There are currently three different controller speeds:

  • 250 Kbits per Second: The slowest speed controller, this type will only support the lowest of the floppy densities; this means the double-density 360 KB 5.25" and 720 KB 3.5" drives. This type of controller is thoroughly, completely obsolete.
  • 500 Kbits per Second: Found on a large number of PCs, the 500 Kbits controller will support all disks except for the 2.88 MB 3.5". This type of controller has been used for many years, although it has in the last few years been mostly replaced by the 1 Mbits/s controller.
  • 1 Mbits per Second: The most modern type, this controller will support all of the floppy disk formats on the market.

Today, the speed of the floppy controller is actually more important when dealing with floppy interface tape drives. In many cases using the full capacity of the tape drive is dependent upon the floppy controller being fast enough to handle the high data transfer rates required by the latest tape formats. This is actually the same exact reason that causes high-capacity floppy formats not to be supported by older, slower controllers.

Tip: You can usually tell what sorts of floppy drives your system will support based on the allowable entries in the floppy drive setup BIOS parameters.

Next: Floppy Disk Controller Resource Usage

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