ATA And SATA Differences

Hard Drives: ATA versus SATA

The performance of computer systems has been steadily increasing as faster processors, memory, & video cards are continuously being developed. The key part that is often neglected when taking a glance at improving the performance of a computer system is the hard drive. Hard drive manufacturers have been constantly evolving the basic hard drive used in modern computer systems for the last 25 years, & the last few years have seen some thrilling developments from faster spindle speeds, larger caches, better reliability, & increased data transmission speeds.

The drive type used most in consumer grade computers is the hearty ATA type drive (often called an IDE drive). The ATA standard dates back to 1986 & is based on a 16-bit parallel interface has undergone lots of evolutions since its introduction to increase the speed & size of the drives that it can support. The latest standard is ATA-7 (first introduced in 2001 by the T13 Technical Committee (the group responsible for the ATA standard)) which supports data transfer rates up to 133MB/sec. This is expected to be the last update for the parallel ATA standard.

As long ago as 2000 it was seen that the parallel ATA standard was maxing out its limitations as to what it could handle. With data rates hitting the 133MB/sec mark on a parallel cable, you are inviting all sorts of issues because of signal timing, EMI (electromagnetic interference) & other data integrity issues; thus industry leaders got together & came up with a used standard known as Serial ATA (SATA). SATA has only been around a few years, but is destined to become "the standard" due to several benefits to be addressed in this Tech Tip.

The technologies that they are going to be taking a glance at are:

ATA (Advanced Know-how Attachment) - a 16-bit parallel interface used for controlling computer drives. Introduced in 1986, it is undergone lots of evolutions in the last 18+ years, with the latest version being called ATA-7. Wherever an item is often called being an ATA tool, it is often a Parallel ATA tool. ATA devices are also often called IDE, EIDE, Ultra-ATA, Ultra-DMA, ATAPI, PATA, etc. (each of these acronyms actually do refer to specific items, but are often interchanged)

SATA (Serial Advanced Know-how Attachment) - a 1-bit serial evolution of the Parallel ATA physical storage interface.

Basic Features & Connections

SATA drives are simple to distinguish from their ATA cousins by the different data & power connections found on the back of the drives. A side-by-side comparison of the interfaces can be seen in this PDF from Maxtor, & the following covers lots of of the differences...

Standard ATA drives, such as this 200GB Western Digital model, have bulky, inch wide ribbon cable with 40-pin data connections & get the 5V necessary to power them from the familiar 4-pin connection. The basic data cables for these drives have looked the same for years. A change was made with the introduction of the ATA-5 standard to better improve the signal quality by making an 80 wire cable used on the 40-pin connector (these are often called 40-pin/80-wire cables). To improve airflow within the computer process some manufacturers resorted to literally folding over the ribbon cable & taping it in to that position. Another recent physical change also came with the advent of rounded cables. The performance of the rounded cables is equal to that of the flat ribbon, but plenty of prefer the improved process air flow afforded, ease of wire management, & cooler appearance that come with them.

SATA drives, such as this 120GB Western Digital model, have a half inch wide, 7 "blade & beam" data connection, which ends up in a much thinner & simpler to manage data cable. These cables take the convenience of the ATA rounded cables to the next level by being even narrower, more flexible & able to being longer without fear of data loss. SATA cables have a maximum length of meter (39.37 inches), which is much greater than the recommended 18 inch cable for ATA drives. The reduced footprint of SATA data connections frees up space on motherboards, potentially allowing for more convenient layouts & room for more onboard features!

A 15-pin power connection delivers the 250mV of necessary power to SATA drives. 15-pins for a SATA device sounds like it would require a much larger power cable than a 4-pin ATA device, but in point of fact the power connectors are the same height. For the time being, plenty of SATA drives are also coming with a legacy 4-pin power connector for convenience.

Plenty of modern motherboards, such as this Chaintech motherboard, come with SATA drive connections onboard (plenty of also including the ATA connectors as well for legacy drive compatibility), & new power supplies, such as this Ultra X-Connect, usually feature plenty of the necessary 15-pin power connections, making it simple to make use of these drives on new systems. Older systems can fundamentally be upgraded to support SATA drives by use of adapters, such as this PCI slot SATA controller & this 4-pin to 15-pin SATA power adapter.

Optical drives are also becoming more available with SATA connections. Drives such as the Plextor PX-712SA take advantage of the new interface, although the performance won't be any greater than a comparable optical drive with an ATA connection.

Performance

In addition to being more convenient to put in & drawing less power, SATA drives have performance benefits that set them apart from ATA drives.

The most fascinating performance feature of SATA is the maximum bandwidth feasible. As they have noted, the evolution of ATA drives has seen the data transfer rate reach its maximum at 133 MB/second, where the current SATA standard provides data transfers of up to 150 MB/second. The general performance increase of SATA over ATA can currently be expected to be up to 5% (according to Seagate), but improvements in SATA know-how will certainly improve on that.

The future of SATA holds great things for those wanting even more speed, as drives with 300 MB/second transfer rates (SATA II) will be available in 2005, & by 2008 speeds of up to 600 MB/second can be expected. Those speeds are brilliant, & are hard to imagine at this point.

Another performance benefit found on SATA drives is their built-in hot-swap capabilities. SATA drives can be brought on & offline without shutting down the computer process, providing a serious benefit to those who cannot afford downtime, or who require to move drives in & out of operation quickly. The higher number of wires in the power connection is partially explained by this, as of the fifteen wires are dedicated to allowing the hot-swap feature.

Cost

Comparing ATA drives to SATA drives can be tricky given all of the variables, but in general it is the case that SATA drives will still cost a bit over a comparable ATA drive. The gap is closing quickly though, & as SATA drives gain in popularity & availability a distinct shift in prices can be expected. Thinking about the benefits of SATA over ATA, the potential difference of a few dollars can fundamentally be justified when thinking about an upgrade. Computer Geeks currently has a limited choice of SATA drives, but several technical sites, such as The Tech Zone & The Tech Lounge, offer actual time cost guides to see how comparable drives stack up.

Final Words

The current SATA standard provides significant benefits over ATA in terms of convenience, power consumption &, most importantly, performance. The main thing ATA has going for it right now is history, as it is been the standard for so long that it won't likely disappear any time soon. The future of SATA will be even more fascinating as speed increases will help hard drive development keep pace with other key process parts.