Select Storage Devices and Hard Drives
You might need to replace a hard drive when it no longer meets your customer's needs for data storage or fails. The signs that a hard drive is failing include
■ Unusual noises
■ Error messages
■ Corrupt data or applications
If your hard drive exhibits any of these symptoms, you should replace it as soon as possible. Figure 11-10 shows Parallel Advanced Technology Attachment (PATA), Serial Advanced Technology Attachment (SATA), and Small Computer System Interface (SCSI) connectors.
ATA was renamed Parallel ATA, or PATA, with the introduction of Serial ATA (SATA). PATA hard drives can use a 40-pin, 80-conductor cable or a 40-pin, 40-conductor cable.
SATA hard drives connect to the motherboard using a serial interface. SATA hard drives have a higher data-transfer rate than PATA drives. The smaller data cable allows improved airflow through the computer case. Early versions of SATA offered a speed of 1.5 Gbps. Current versions offer a speed of 3.0 Gbps.
The SCSI standard is typically used for hard drives and for tape storage. However, printers, scanners, CD-ROM drives, and DVD drives can also use SCSI. Today, SCSI devices are used mostly on servers or computers that require high transfer speeds and reliability.
Figure 11-10 Hard Drive Connectors
SCSI is a more advanced interface controller than PATA or SATA. It is ideal for high-end computers, including network servers. Devices can include hard drives, CD-ROM drives, tape drives, scanners, and removable drives. SCSI devices are typically connected in a series, forming a chain that is commonly called a daisy chain, as shown in Figure 11-11. Each end of the daisy chain must be terminated to prevent signals from bouncing off the ends of cables and causing interference. Generally, the SCSI controller on one end of the SCSI bus has on-board termination. The other end of the SCSI cable is either terminated by a resistor on the last drive on the chain or a physical terminator on the end of the SCSI bus.
Figure 11-11 SCSI Daisy Chain
Most SCSI buses can handle a total of seven devices and a SCSI controller. The channels are numbered from 0 through 7. Some versions of SCSI support a total of 15 devices plus the SCSI controller. These channels are numbered 0 through 15. Each device on a SCSI channel must have a unique SCSI ID. For example, the primary drive would be 0 and the controller card is usually 7. The SCSI ID is generally set by jumpers on a SCSI drive.
The SCSI bus was originally 8 bits wide and operated at a transfer rate of 5 MBps. Later SCSI technologies used a 16-bit bus and operated at 320-640 MBps. Table 11-1 shows the different types of SCSIs. Current and future SCSI technologies use a serial interface for increased speed.
|
SCSI Type |
Also Called |
Connector |
Maximum Throughput (MBps) |
|
SCSI-1 |
— |
50-pin |
|
|
Centronics 50-pin |
5 |
||
|
Fast SCSI |
Plain SCSI |
50-pin |
|
|
Centronics 50-pin |
10 |
||
|
Fast Wide SCSI |
— |
50-pin |
|
|
68-pin |
20 |
||
|
Ultra SCSI |
Fast-20 |
50-pin |
20 |
|
Ultra Wide SCSI |
— |
68-pin |
40 |
|
Ultra2 SCSI |
Fast-40 |
50-pin |
40 |
|
Ultra2 Wide SCSI |
— |
68-pin |
|
|
80-pin |
80 |
||
|
Ultra3 SCSI |
Ultra-160 |
68-pin |
|
|
80-pin |
160 |
||
|
Ultra320 SCSI |
— |
68-pin |
|
|
80-pin |
320 |
Narrow SCSI is 8 bits wide and Wide SCSI is 16 bits wide. Narrow SCSI uses 50-pin connectors and Wide SCSI uses 68-pin connectors. Internal connections use 80-pin connectors.
Continue reading here: Upgrade and Configure a Motherboard
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