SUMMARY

Now that you've finished chapter 8, you should be able to describe the (1) characteristics of floppy and hard disks, (2) methods for encoding digital data onto magnetic disks, (3) disk drive transports and their preventive maintenance requirements, (4) parts of a disk drive's electronics component, and (5) common types of disk drive interface electronics. The following is a summary of important points in this chapter:

FLOPPY DISKS are single-sided or double-sided plastic disks coated with oxide particles. The disks can be single-density, double-density , or high density.

Data is stored on floppy disks in CIRCULAR TRACKS. The tracks are divided into arcs called SECTORS.

HANDLE, SHIP, and STORE floppy disks carefully. Contaminates between the heads and the disk surface can cause serious damage.

FIXED (HARD) DISKS are aluminum platters coated on both sides with iron oxide or thin-film metal. Most hard disk drives use disk packs which are several disk platters stacked together. Some hard disk drives use removable disk platters. Either the CYLINDER OR SECTOR METHOD is used to place data on hard disks.

HANDLE, STORE, AND SHIP HARD DISKS with extreme care. Contaminates on the heads or the disk surface can cause head-crash.

ERASE HARD AND FLOPPY DISKS by reformatting or degaussing.

Three popular METHODS FOR ENCODING DIGITAL DATA ONTO DISKS are frequency modulation, modified frequency modulation, and run length limited.

FLOPPY DISK DRIVE TRANSPORTS contain the parts that (1) spin the floppy disk, (2) write data to the disk, and (3) read data from it.

The DRIVE MOTOR/SPINDLE ASSEMBLY of a floppy disk drive transport holds and spins the floppy disk. The transport's HEAD ARM ASSEMBLY holds the read/write heads and its ACTUATOR ARM ASSEMBLY positions the heads over the disk's recording surface.

HARD DISK DRIVE TRANSPORTS contain the parts that (1) rotate the hard disk platter, (2) write data to the disk, and (3) read data from the disk.

The DRIVE MOTOR/SPINDLE ASSEMBLY of a hard disk drive transport holds the disk pack in place while the drive motor spins the spindle at 3600 RPM. The transport's HEAD ARM ASSEMBLY holds the read/write heads and its ACTUATOR

ARM ASSEMBLY positions the heads over the correct track of the hard disk.

FLOPPY DISK DRIVES REQUIRE PREVENTIVE MAINTENANCE at regular intervals because they are not sealed units and the disks use an oxide coating that wears off and sticks to the heads and other parts.

HARD DISK DRIVES REQUIRE VERY LITTLE PREVENTIVE MAINTENANCE. Cartridge disk drives will have a special cleaning kit for doing the preventive maintenance.

Magnetic DISK DRIVE ELECTRONICS consist of (1) control electronics to control the electromechanical parts of a disk drive, (2) write/read electronics to write data to and read data from a disk drive, and (3) interface electronics to interface the disk drive to the host computer.

MAGNETIC DISK RECORDING SPECIFICATIONS are set by the manufacturer; all you can do is measure them. Six of the most common specifications are seek time, latency period, access time, interleave factor, transfer rate, and recording density.