CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [165]
SATA is backward compatible with current PATA standards and enables you to install a parallel ATA device, including a hard drive, optical drive, and other devices, to a serial ATA controller by using a SATA bridge. A SATA bridge manifests as a tiny card that you plug directly into the 40-pin connector on a PATA drive. As you can see in Figure 11-20, the controller chip on the bridge requires separate power; you plug a Molex connector into the PATA drive as normal. When you boot the system, the PATA drive shows up to the system as a SATA drive.
Figure 11-20 SATA bridge
SATA’s ease of use has made it the choice for desktop system storage, and its success is already showing in the fact that more than 90 percent of all hard drives sold today are SATA drives.
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EXAM TIP As this book went to press, a few motherboards and hard drive controller cards appeared that support the SATA 3.0 standard, with data rates up to 6 GBps. Look for the SATA 3.0 drives on the store shelves after you read this, but don’t expect the technology to be on the CompTIA A+ exams this time around.
AHCI Windows Vista and later operating systems support the Advanced Host Controller Interface (AHCI), a more efficient way to work with SATA HBAs. Using AHCI unlocks some of the advanced features of SATA, such as hot-swapping and native command queuing.
When you plug in a SATA drive to a Windows computer that does not have AHCI enabled, the drive doesn’t appear automatically. You need to go to the Control Panel and run the Add New Hardware Wizard to make the drive appear. AHCI makes the drive appear in Computer, just what you’d expect from a hot-swappable device.
Native command queuing (NCQ) is a disk-optimization feature for SATA drives. It enables faster read and write speeds.
AHCI is implemented at the CMOS level (see “BIOS Support” later in this chapter) and generally needs to be enabled before you install the operating system. Enabling it after installation will cause Vista to Blue Screen. Nice.
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NOTE If you want to enable AHCI but you’ve already installed Windows Vista, don’t worry! Microsoft has developed a procedure (http://support.microsoft.com/kb/922976) that will have you enjoying all that AHCI fun in no time. Before you jump in, note that this procedure requires you to edit your Registry, so remember to always make a backup before you start editing.
eSATA External SATA (eSATA) extends the SATA bus to external devices, as the name would imply. The eSATA drives use connectors similar to internal SATA, but they’re keyed differently so you can’t mistake one for the other. Figure 11-21 shows eSATA connectors on the back of a motherboard. External SATA uses shielded cable lengths up to 2 meters outside the PC and is hot pluggable. The beauty of eSATA is that it extends the SATA bus at full speed, so you’re not limited to the meager 50 or 60 MBps of FireWire or USB.
Figure 11-21 eSATA connectors
If a desktop system doesn’t have an eSATA external connector, or if you need more external SATA devices, you can install an eSATA HBA PCIe card or eSATA internal-to-external slot plate. You can similarly upgrade laptop systems to support external SATA devices by inserting an eSATA ExpressCard (Figure 11-22). There are also USB to eSATA adapter plugs, although you’ll be limited to the much slower USB data-transfer rates. Install eSATA PCIe, PC Card, or ExpressCard following the same rules and precautions for installing any expansion device.
Figure 11-22 eSATA ExpressCard
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NOTE For the scoop on PC Cards and ExpressCards—both technologies designed to add expansion options for portable computers—see Chapter 21, “Portable Computing.”
SCSI: Still Around
Many specialized server machines and enthusiasts’ systems use the small computer system interface (SCSI) technologies