IDE Technology, high-level format

Reduced write current means just what it says. At some cylinder near the center of the platter, the read/write heads reduce the current used to place magnetized spots on the disk because the spots are getting closer and closer together. Reduced write current is not as common as write pre-compensation.

IDE Technology

The following figure shows a hardware subsystem including an IDE (Integrated Device Electronics) hard drive and its adapter card. In addition to the connection for the cable, the hard drive has a connection for the power cord from the power supply. The controller for the hard drive is mounted on a circuit board on the drive housing. This arrangement makes it possible for the controller and the hard drive to work in ways that are quite different from older MFM and RLL technology to low-level format the drive and store data.

The controller mounted directly on the drive case communicates with the system bus by means of an adapter card. An adapter card is a card that merely receives data from the hard drive controller and passes it along to the system bus. An adapter card does little else but pass data along, and is, therefore, inexpensive. The controller and the adapter card are connected with a single 40-pin cable. Sometimes an adapter card connects a hard drive to a system board to compensate for the system board BIOS not supporting a large-capacity drive. The adapter card contains the necessary BIOS to support the drive in place of the system BIOS.

The older MFM and RLL technologies use either 17 or 26 sectors per track over the entire drive platter. The larger tracks near the outside of the platter contain the same number of bytes as the smaller tracks near the center of the platter. This arrangement makes first formatting a drive and later accessing data simpler, but it wastes drive space. The number of bytes that a track can hold is determined by the centermost track, and all other tracks are forced to follow this restriction. The formatting of IDE drives eliminates this restriction. The number of sectors per track on an IDE drive is not the same throughout the platter. In this new formatting system, called zone bit recording, tracks near the center have the smallest number of sectors per track, and the number of sectors increases as the tracks get larger. In other words, each track on an IDE drive is designed to have the optimum number of sectors appropriate to the size of the track. What makes this arrangement possible is that every sector on the drive still has 512 bytes.

Since the track and sector markings on IDE drives do not follow a simple pattern, they

are written on the hard drive at the factory. This process is called low-level formatting.

The operating system still executes the remainder of the format process (creating a boot sector,

FAT, and root directory), which is called the high-level format or OS format.

Because IDE drives are low-level formatted by the manufacturer, they cannot be low-level

formatted as part of preventive maintenance, as older drives can be. The track and sector

markings on the drive created at the factory are normally expected to last for the life of the drive. For this reason IDE drives are often referred to as disposable drives. When the track and sector markings fade, you just throw the drive away and buy a new one. Improvements for formatting the IDE drive are becoming more commonplace. Some better-known IDE drive manufacturers are offering a low-level format program specific to their drives. If an IDE drive continues to give “Bad Sector or Sector Not Found” errors or even becomes unusable, ask the manufacturer for a program to perform a low-level format of the drive. Sometimes these programs are only distributed by the manufacturer to dealers, resellers, or certified service centers.