Monday, June 11, 2007

PATA VS SATA

Parallel ATA (PATA) has been the industry standard for connecting hard drives and other devices in computers for well over a decade. However, due to a few major limitations, PATA could be a quickly dying breed with the introduction of Serial ATA (SATA). To compare, PATA cables are limited to only 18 inches long, while SATA cables can be up to 1 meter in length, which is less than 40 inches. It is possible to have longer cables but, due to attenuation, these longer cables are generally more trouble than they are worth.

PATA cables are large and bulky and can easily restrict airflow. With the onslaught of better and faster devices, computers continue to generate more heat and this can cause many problems including complete computer failure. PATA cables are 40 wires wide and they block precious space, which can restrict airflow greatly. SATA cables are only 7 pins wide and, with their longer maximum length, can be easily routed to not restrict any airflow at all. The change to serial transfer is what allows the cable to be so thin, only two data channels are required, one for sending and one for receiving data. Parallel cables use multiple wires for both sending and receiving and this technology uses a total of 26 wires for data transfer.

Another comparison is that SATA devices require much less power than PATA. Chip core voltages continue to decline and, because of this, PATA's 5-volt requirement is increasingly difficult to meet. In contrast, SATA only requires 250 mV to effectively operate. SATA is also hot-swappable meaning that devices can be added or removed while the computer is on (depends on OS features to detect new hardware after hot-swap).

The last, and most important, difference is the maximum bandwidth between the two technologies. The true maximum transfer rate of PATA is 100 MB/sec with bursts up to 133 MB/sec. With the first introduction of SATA, the maximum transfer rate is 150 MB/sec. This is supposed to increase every 3 years with a maximum transfer of 300 MB/sec in 2005 and 600 MB/sec in 2008. Finally, SATA doesn't require any changes to existing operating systems for implementation. SATA is 100% software compatible and, with SATA adapters, some hardware doesn't have to be immediately replaced.

Parallel ATA

Serial ATA

Maximum Speed

100 MB/s with bursts up to 133 MB/s

300 MB/s and 600 MB/s by 2008

Cable Length

18 Inches

1 Meter (about 40 inches)

Cable Pins

40

7

Power Connector Pins

4

15

Data transfer wires used

26

2

Power Consumption

5V

250 mV

Hot Swappable?

No

Yes

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