A Guide to Serial ATA
SATA and SATAII hard drive interfaces


A Guide to Serial ATA


If you have looked at computer store shelves lately, you have probably noticed that SATA drives are becoming more prevalent. Most motherboards now come standard with at least two SATA connectors, most power supplies have SATA power connectors built in, and SATA hard drives are becoming cheaper and more available. SATA I (SATA 150) has been around for a while, and now SATA II (SATA 300) is becoming prevalent, but SATA in general has lately come into much wider use. While PATA has not been entirely phased out, SATA has begun its takeover. This article will explain the differences between parallel and serial technology and show you the features SATA has to offer. It will also show you what is to come in the SATA world


SATA: A Brief History
SATA, or Serial ATA, has been around for some time. While you may have only noticed it in the past few years, the Serial ATA 1.0 Working Group was formed in February 2000 to design SATA for desktops. Then, in 2002, the Serial ATA II Working Group was established to work with SATA on servers and networks and to create the next generation of transfer speeds. In July 2004, the SATA International Organization (SATA-IO) was officially formed. SATA-IO “provides the industry with guidance and support for implementing the SATA specification,” according to their website. (http://www.sata-io.org)

Dispelling the Confusion: SATA II does not mean 3Gb/s

The term SATA II has grown in popularity as the moniker for the SATA 3Gb/s data transfer rate, causing great confusion with customers because, quite simply, it’s a misnomer.

The first step toward a better understanding of SATA is to know that SATA II is not the brand name for SATA’s 3Gb/s data transfer rate, but the name of the organization formed to author the SATA specifications. The group has since changed names, to the Serial ATA International Organization, or SATA-IO.

The 3Gb/s capability is just one of many defined by the former SATA II committee, but because it is among the most prominent features, 3Gb/s has become synonymous with SATA II. Hence, the source of the confusion.

For an accurate description of Serial ATA capabilities and the official guideline to SATA product naming, please see the details below.





Parallel vs. Serial
To truly understand the power of Serial ATA, we must first understand its predecessor, Parallel ATA. Parallel ATA (PATA) has been the standard for quite some time now, but has many problems. First, IDE cables, as you have surely noticed, are large and very hard to arrange in cases. SATA cables are much easier to use and arrange in cases because they are very small and take up very little space. SATA cables have only seven wires (compared to 40 wires with PATA), making them smaller and thus easier to use. This is due to the way SATA transfers data. In a method called serializing, SATA divides up the bits in a byte and sends them one at a time. This seems like a slower way of doing things, but since SATA cables are shielded, they suffer from very little interference. Because there is very little interference, serial cables (like Ethernet cables) can travel very long distances with little speed drop.

As you can see SATA has a great advantage over PATA. However, the list of advantages does not stop here. Keep reading to find out what else SATA has to offer.


Advantages of SATA

As mentioned before, there are many advantages of SATA. The most prominent being speed. PATA has a max burst speed of only 133MB/sec. SATA I has speeds of about 150MB/sec, not much faster, but SATA II has speeds of close to 300MB/sec. That is over double of the fastest PATA drives. SATA is clearly faster than PATA, but there are a few more benefits of SATA.

As said before, SATA cables have only seven wires. This makes them much easier to work with when wiring computer cases. Having less space taken up by cables makes it easier to have more hard drives. Also, airflow is improved because there is less air being blocked by the drive cables.

Another advantage is that SATA is that it is backwards compatible (so is PATA, but that's not what we’re here for). So if you have a SATA II hard drive and a SATA I motherboard, you can use them together. However, you will only get speeds of SATA I. The same is true for the reverse. If you have a SATA I hard drive and a SATA II motherboard, you will still only reach speeds of SATA I.

Other advantages include no tiny jumpers that you have to configure for your drives to work right. SATA has no master/slave configuration which makes for easier setup. SATA cables can also reach up to one meter (3ft.), which gives builders a lot more freedom for cable management and drive placement.


Disadvantages of SATA
There are very few disadvantages of SATA. The main disadvantage, however, is cost. As with any new technology, SATA costs slightly more then its predecessor. While the costs are becoming closer and closer by the day, SATA still has a bit of a higher price tag.


What's to Come?

SATA has certainly become a standard in modern computers, exceeding the speeds of its predecessor, PATA, twofold. SATA also looks like it will have promising future in the computer industry. Word has it that by 2007, SATA III will be released. It is expected to have speeds around 600MB/sec. Most likely, the price will be fairly high, but with speeds like that, many will go for the 3rd generation of SATA.