Virtually every PC today relies on the venerable ATA (Advanced Technology Attachment) interface to connect hard drives, CD drives, and other types of drives. Spurred by the relentless demands for faster drive performance and greater reliability, the ATA standard (also known as IDE), which has a rated connection speed of 3.3 MBps, has undergone many advances. The Ultra ATA (dubbed Ultra ATA/133) interface can pass 16 bits of parallel data between a drive and PC at speeds of up to 133 MBps.
Such parallel-signal schemes, however, are reaching the practical limits of current cable, drive, and controller electronics. To achieve even faster data transfer rates, drive manufacturers are turning to a serial scheme called Serial ATA (SATA). Though it may seem counterintuitive that a serial technology (which transfers data one bit at a time rather than transferring multiple data bits simultaneously, as a parallel scheme does) could outpace a parallel one, that's exactly what SATA does; it transfers data at a much faster rate and more efficiently. Now that SATA drives, add-in controller cards, and most importantly, PC chipsets are finally available, you'll want to understand the benefits of this technology.
SATA typically handles data transfers of up to 150 MBps and in the future can be scaled up to 300 MBps and beyond. Some manufacturers predict speeds as high as 600 MBps. SATA offers a speedier boot process and faster loading of programs and data. But perhaps the best part of the new technology is SATA's simpler cabling.
If you've ever looked inside a PC, you've seen the wide, gray, 40-pin ribbon cable that daisy-chains master/slave drives to the ATA controller port. Not only were those 40 wires laying close together a potential source of interference, but routing the bulky cable made the placement of drives difficult. Moreover, the traditional cables are notorious for disturbing air flow within PCs. SATA uses thin cables that route easily and don't block a PC's cooling system, thus preventing hot spots and improving overall system reliability.
Connecting SATA drives is easier, too. Each drive connects to the host PC via an individual cable; the host PC treats all drives as master devices, eliminating the jumper settings, which have frustrated users for years. This greatly eases installation and configuration. Finally, the cables can be longer. Current parallel ATA cables max out at 18 inches, while SATA cables can be as long as 39.4 inches (1 meter). That's good for high-end boxes that use full-tower cases.
You will also find adding or replacing drives easier with SATA. You won't have to power down your PC before connecting a new drive, because SATA allows for hot-pluggable connections, so you can add or remove SATA drives while your PC is running. The connectors are also keyed (that is, designed for one-way insertion), so you don't need to worry about accidentally reversing a connection.
SATA is software-compatible with ATA, so you don't need any special drivers or OS upgrades to support the new drives; the SATA controller does the conversion between the drive and host PC. Consequently, SATA drives can coexist on the same system with parallel ATA devices.
Yet because of the differences between SATA and parallel ATA, you can't simply drop a SATA drive into a parallel ATA system. Here's what it takes to implement Serial ATA on your PC.
To start, you'll need a new SATA drive such as the 120GB Seagate Barracuda ATA V (
www.seagate.com). The only difference you'll see in the SATA drive is the connector scheme (and the absence of drive jumpers).
The host PC requires a SATA controller with one or more SATA ports, such as the Promise Technology SATA150 TX2plus, which combines two independent SATA ports and one Ultra ATA port and supports up to two serial and two Ultra ATA drives (
www.promise.com). In new SATA-compatible machines, the motherboard uses a controller chip that supports SATA. The Marvell 88i8030 Serial ATA Bridge Chip (
www.marvell.com) is one accepted device available for developers, and integrated chipsets supporting SATA are expected from leading chipset makers including ALi Corp. (
www.ali.com.tw), Intel Corp. (
www.intel.com), and VIA Technologies (
www.via.com.tw).
