The Difference Between IDE & SATA II Hard Drive

Written by aj graham
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The Difference Between IDE & SATA II Hard Drive

Hard drive technology has had many changes over the years. Entire floors of office buildings used to be dedicated to storing the amount of data that can now fit easily in your pocket. In recent years, hard drive technology has changed once again. IDE or Parallel ATA drives have been replaced by the new standard, Serial ATA or SATA. SATA has a few iterations of drives, SATA and SATA II. SATA drives offer many improvements over IDE drives.


IDE and SATA drives are not interchangeable without an adaptor. IDE drives use a 40-pin ribbon cable that can connect up to two drives. SATA uses a much smaller 7-pin cable that will only allow for one drive connection. The IDE interface runs in parallel while SATA interface runs in serial. Parallel connections are when data is sent in groups as compared to serial connections with a single stream of data. When data is sent in parallel connections, the receiving end will have to wait for all streams of data to arrive before it can be processed; however, serial connections are able to have the data streamed with just one connection and eliminate the delay.

Power Connection

IDE drives use a standard 4-pin Molex power connection found on virtually all computer power supplies. SATA drives use a new power connection that has a 15-pin connector. The SATA has a new power connection for a number of reasons. Instead of the standard 5v or 12v in the Molex connector, SATA power connectors also have a 3.3v line. The SATAs' new power connector also allows for hot-plugging or plugging in the power while the computer is on. This is accomplished by having a ground contact that is longer so it connects first.

Data Transfer Rates

Since SATA drives are newer, they have newer technology. IDE drives range in data transfer rates from 33 MB/s to 133 MB/s. SATA drives are available in data transfer rates of 150 MB/s for SATA I and 300 MB/s for SATA II. Data transfer rates are not the only gauge for speed when it comes to hard drives. Hard drive seek time is also an important factor to think of when comparing speeds of drives. Hard drive seek time depends on the drive itself and is not limited by the type of interface.

Command Queuing

One of the biggest benefits of SATA and SATA II drives over IDE is the ability for the SATA drive to have multiple commands within the drive simultaneously. SATA drives will store commands up to perform them in a much more logical path based on speed and performance instead of which command was first. IDE drives operate on a FIFO method for handling commands. FIFO stands for First In, First Out. IDE drives will perform commands in the order that they are received.

Hot Swapping

SATA drives have the ability to be hot swappable. Since the SATA and SATA II drives use a new type of power connector, they are able to be plugged in while the computer or power supply is on. IDE drives can only be used as a hot swappable drive if they are used inside of a hot swappable adaptor. IDE drives do not have this functionality built in.

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