I recently had to install a new hard drive in a computer that was about 2 years old. Before purchasing the new hard drive I needed to determine the interface the hard drive uses. There are currently two interfaces in existence today: PATA (IDE or EIDE) and SATA.
For newer computers, you will probably find SATA, while in my particular instance it was PATA. In this post I discuss both PATA and SATA by provided a brief background, the different ATA specifications and how devices are connected to each interface.
History of ATA?
ATA, like many computer terms, is an acronym for Advanced Technology Attachment and is the standard interface for storage devices such as hard drives and CD-ROMs in a computer. Other terms such as IDE (Integrated Drive Electronics) and EIDE (Enhanced IDE) have been used interchangeably with ATA.
In 1986, Western Digital developed an early specification known as IDE because of the drive controller on the drive itself instead of on the motherboard. Later EIDE was developed as an extension of ATA to allow support for drives larger than 528MB up to 8.4GB.
As the years went on more storage devices were able to use the ATA interface. These devices include CD/DVD-ROMs and tape drives.
For many years, ATA interfaces used long ribbon-like cables for transmitting data. Each cable consisted of 40 pins and 40 wires for transferring each bit of information. In the later years of ATA, the number of wires increased to 80 with the additional 40 wires becoming ground wires. This provided more shielding between the wires once the data transfer rates increased to over 66MB/s.
The image below shows a PATA cable.
Around 2003 a new standard came on the market SATA or Serial ATA. This in turn caused the previous ATA interfaces to be rename PATA (Parallel ATA). The one noticeable difference between the two is the size of the cable. PATA needed a much wider cable to transmit the data because of the number of wires, while the SATA cable is much thinner since fewer wires are needed.
An example of a SATA cable is shown below.
ATA Standards
Over the years the ATA standard as evolved with support for higher capacities and faster transfer rates. The table below outlines these standards:
| Standard | Other Names | Speeds | Notes |
|---|---|---|---|
| ATA-1 | ATA, IDE | PIO (Programmed I/O) Mode 0 – 3.33MB/s PIO Mode 1 – 5.22MB/s PIO Mode 2 – 8.33MB/s DMA (Direct Memory Access) Mode 0 – 2.08MB/s DMA Mode 1 – 4.17MB/s DMA Mode 2 – 8.33MB/s | The size limit of this standard was 137GB. |
| ATA-2 | EIDE, Fast ATA, Fast IDE, Ultra ATA | PIO Mode 3 – 11.11 PIO Mode 4 – 16.67MB/s DMA Mode 0 – 4.17MB/s DMA Mode 1 – 13.33MB/s DMA Mode 2 – 16.67MB/s | |
| ATA-3 | EIDE | Same as ATA-2. | |
| ATA-4 | Ultra ATA/33 | UDMA (Ultra DMA) Mode 0 – 16.67MB/s UDMA Mode 1 – 25.00MB/s UDMA Mode 2 – 33.33MB/s | The speed of this standard was 33MB/s. The transfer method is also known as UDMA/33. |
| ATA-5 | Ultra ATA/66 | UDMA Mode 3 – 44.44MB/s UDMA Mode 4 – 66.67MB/s | The speed of this standard was 66MB/s. The transfer method is also known as UDMA/66. |
| ATA-6 | Ultra ATA/100 | UDMA Mode 5 – 100MB/s | The speed of this standard was 100MB/s. The transfer method is also known as UDMA/100. |
| ATA-7 | Ultra ATA/133 SATA/150 | PATA – 133MB/s SATA – 150MB/s | The transfer method is also known as UDMA/133. The first version of the SATA interface is also part of this standard. |
Multiple Storage Devices
Each PATA cable can connect two storage devices – one master and one slave. This means that a cable can have a single master connected to it, or a master and slave or simply cable select. Since each drive has its own controller, you must specifically tell one of the drives to be the master and the other to be the slave.
Motherboards that support PATA usually have a primary and secondary channel to allow for up to four devices to be installed (two for each channel). In this case the main hard drive with your operating system is usually set as the master on the primary channel.
Setting up storage devices on a SATA interface is much simpler since the master/slave or cable select settings are no longer necessary.
Summary
There are currently two internal storage devices in use in today’s home computers: PATA and SATA. Most new computers sold today use the SATA interface, as the PATA interface is now older technology that has reached its speed potential. There are many ATA specifications with each adding the support for larger capacities and faster transfer rates.
When connecting two devices to a PATA cable, you must ensure that one drive is set to master and the other is set to slave. With SATA, it is much simpler as the master/slave settings are no longer needed.