CHAPTER SUMMARY

§ Hard drive capacity is determined by the number of heads, tracks, and sectors on the disk, each sector holding 512 bytes of data.

§ System BIOS and software can use CHS, large mode, or LBA mode to manage a hard drive. The size of the drive normally determines which mode is used.

§ Some older systemboard BIOS does not support larger capacity drives. You can solve the problem by upgrading BIOS, upgrading the systemboard, or using software designed to interface between the drive and the BIOS.

§ The FAT or file allocation table lists all clusters on the hard drive and how each is allocated.

§ A directory on a hard drive holds the information about each file stored on the drive. The main directory created when the drive is first formatted is called the root directory.

§ Commands to manage a hard drive include those to create and remove directories change the attributes on a file, and list paths where the OS can look to find software. DOS, Windows 3.x, and Windows 95 all offer commands or menu options to perform these tasks.

§ Some ways to optimize drive space and access speed are to reduce fragmentation, to compress the drive, and to use disk caching.

§ Older hard drives use either MFM or RLL technology. Most hard drives for PCs today use IDE technology. SCSI hard drives refer more to the bus used by the drive than the technology of the drive.

§ There are several variations of SCSI buses and bus devices including SCSI-1, SCSI-2, CSI, and Ultra SCSI.

§ Every SCSI bus subsystem requires a host adapter with a SCSI controller and SCSI Ids assigned to each device including the host adapter.

§ Each end of the SCSI bus must have a termination resistor, which can be either hardware or software.

§ There are three technologies used by removable drives: magnetic media, optical or magneto-optical, and phase dual.

§ Removable drives vary considerably in cost per KB of storage, drop height, half-life of the data, interfaces to the CPU, and other features.

§ External removable drives use either a parallel port or a SCSI port to interface with the CPU.