The cables that connect hard drives to computers -- and the ports on both the hard drives and the motherboards themselves -- are the product of standards. In the early 2000s, one of the fundamental standards for connecting hard drives to computers changed, from IDE hard drives – later called PATA, standing for Parallel AT Attachment – to SATA, standing for Serial AT Attachment. In both acronyms, "AT" stands for the AT form factor of PC motherboards.
History of PATA/IDE
PATA, also called ATA or IDE, was developed in the early 1980s as a unified standard for moving data between hard drives -- and similar devices, like CD-ROM drives in the 1990s -- that went through several incremental upgrades, including speed upgrades to ATA-33, ATA-66 and UATA-133, which was its final incarnation. While there are still a handful of PATA drives on the market as of December 2012, they exist primarily for markets where low power consumption is more important than performance. While SATA drives were more expensive when first introduced in 2003, they are now comparable, or in many cases, less expensive than PATA drives of the same capacity. More importantly, new motherboards rarely have PATA connectors on them.
Inside the computer's case, you can see an obvious difference between PATA and SATA hard drives: the connectors. PATA connectors are flat ribbon cables with 40 or 80 wires. SATA connectors are much smaller and the cables are thinner; they're also easier to install and produce less case clutter. While there are PATA-to-SATA adapter cables, hard drives are generally cheap enough, and grow in capacity quickly enough, that it's easier to migrate your data from an old PATA drive to a SATA drive than to put an adapter cable in.
PATA has a peak data transfer rate of 133 gigibits per second, which roughly translates to 133 megabytes of data transferred each second. SATA has gone through three generations since its widespread introduction in 2002. First-generation SATA has a data-transfer rate of 150 Gbps, second generation SATA has a data-transfer rate of 300 Gbps, and third generation has a data-transfer rate of 600 Gpbs. On top of this, because SATA drives are generally newer, and built with more recent technology, they spin at higher RPMs -- decreasing seek times -- and have much higher capacities. When SATA was first introduced, few home computers had hard drives, or system buses, capable of using the full speed. With modern hardware, upgrading to a higher-speed hard drive with a faster SATA interface can give noticeable performance boosts.
Other SATA Features
SATA moves information about the capacity and addressing information about the drive from the computer's BIOS to a chip that's on the drive itself; this means that the days of being forced to partition the hard drive into chunks small enough for the BIOS to recognize are gone. SATA drives are also hot-swappable; you can unplug a SATA drive from a computer without powering it down, and swap it for a different one, which is a feature that's very handy for server administrators, and people who do mirroring backups and need to rotate backup drives. SATA has also spawned the eSATA standard, which is a specification that uses an external SATA port and a shielded cable of up to six feet to run a high speed external hard drive, and provides faster throughput than USB or FireWire.
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