Hardware Reference
In-Depth Information
Floppy Drive Interfaces
Floppy drives are interfaced to the PC in several ways. The standard interface that all PC
floppy disk drives use is called the Shugart Associates SA400 interface. It was invented
in the 1970s and is based on the NEC 765 controller chip. All modern floppy controllers
contain circuits that are compatible with the original NEC 765 chip. This industry-stand-
ard interface is why you can purchase drives from almost any manufacturer and they will
all be compatible.
Because the traditional floppy controller only works internally, external floppy drives are
generallyinterfacedviaUSB.USBfloppydrivesoftenhaveastandardfloppydriveinside
anexternalboxwithaUSB-to-floppycontroller.Newerlegacy-freesystemsdon'tinclude
a traditional floppy controller, so if a floppy drive is desired, it would generally have to
be a USB external model. In the past, some drives have been available in FireWire (IEEE
1394) or even parallel interfaces.
Drive Components
All floppy disk drives, regardless of type, consist of several basic common components,
each of which are detailed in the following sections.
Read/Write Heads
A floppy disk drive usually has two read/write heads—one for each side of the disk, with
both heads being used for reading and writing on their respective disk sides (see
Figure
such drives), but today single-sided drives are a faded memory.
Figure 10.5
A double-sided drive head assembly.
