Com 226 comp trouble shooting II theory book
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| Platters and Media Where floppy disks use magnetic material applied over a thin, flexible substrate of mylar (or some other plastic, hard drives use rugged, solid substrates, called platters. You can clearly view the platters of a hard drive in Fig. 17-2. A platter is traditionally made of alu- Power-Mode Definitions Modern hard drives are not simply on or off They operate in anyone of several modes, and each mode makes different power demands on the host system. This is particularly important because today’s PCs are becoming evermore power conscious, so the ability to control drive power is an integral part of PC power-conservation systems. Typical hard drives operate in any of five different power modes - Spin-up The drive is spinning up following initial application of power and has not yet reached full speed. This demands about 14 Wand is particularly demanding of the power supply (if the supply is marginal or overloaded, the hard drive might not spin-up properly. - Seek This is a random-access operation by the disk drive as it tries to locate the required track for reading or writing. This demands about 8.5- to 9.0 W. - Read/write A seek has been completed, and data is being read from or written to the drive. This uses about 5.0 W. - Idle This is a basic power-conservation mode, where the drive is spinning and all other circuitry is powered on, but the head actuator is parked and powered off. This drops power demands to about 4 W, yet the drive is capable of responding to read commands within 40 ms. - Standby The spindle motor is not running (the drive spins down. This is the main power-conservation mode, and it requires just 1 W. It might require up to several seconds for the drive will leave this mode (or spin-up) upon receipt of a command that requires disk access. Download 1.89 Mb. Share with your friends:
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