What is a
Hard Drive Interface?

The hard drive interface is the computer bus that connects the hard disk drive to the processor and memory. There are two types of hard drive interfaces: the internal interface and the external interface. Understanding interfaces can help you on your next hard drive purchase. Whether you want the fastest interface or you just want the cheapest hard drive, this knowledge will help you in your decision making.

Personal computers have the following types of interfaces:

• IDE/PATA - A parallel interface with a wide ribbon cable. It connects to the IDE Hard Drive. The fastest parallel ATA drive is the Ultra ATA133 EIDE Hard Drive.



• SATA - This is the serial interface that replaces PATA. The current top speed of the SATA hard drive is 300 MB/s with 600 MB/s hard drives just around the corner. SATA has a separate standard for external SATA hard drives called eSATA.



• USB - Universal Serial Bus. A highly popular external interface for hard drives and other devices. This interface is found on all modern notebooks and desktop PCs. Even at the fastest speed, this interface is still rather slow for a hard drive.



• FireWire - This external interface is used mostly by Macs. Very few PC motherboards support this interface anymore. If your motherboard doesn't support it, you have the option of buying a PCI Firewire adapter card. Firewire 800 is nearly twice as fast as USB 2.0 and it can be daisy-chained.



• SCSI - This hard drive interface is both external and internal. It used to be the interface of choice with the Macs but it has long since been replaced by Firewire. Currently, this interface is mostly used in Enterprise Applications for storage systems that need to stay up 24x7.



• SAS - Serial Attached SCSI. This interface purported to replace traditional SCSI (Parallel SCSI). It will likely cost less than parallel SCSI but it will never be as cheap as SATA. If you want this interface, you will need to purchase a SAS PCI adapter card.



• PCMCIA - This interface is used in portable computers. It defines a form factor that can include a hard drive, wireless adapter, or bus adapters.



• PCI - Peripheral Connect Interface. This is an internal interface bus used on almost all computers today. It enables you to connect to interfaces that may not be supported by your motherboard. It can also be used to get extra ports when you've used up all the ones provided by the motherboard.



• Network - Sometimes just called Ethernet. This is just another way to hook up a hard drive to your computer. Sharing your hard drive is easy when the drive is a network disk.

Interface Selection Guidelines

The hard drive isn’t the only storage device that uses these interfaces. Other storage devices such as CDROMs, DVDs, and Tapes, also connect to these interfaces.

Your performance goals are a big factor in deciding which interface to use. If you want high performance you would pick SCSI or SAS. If you desire portability, than USB or FireWire are a good choice. IDE/PATA is the choice for backward compatibility. SATA is the best hard drive interface for a general purpose computer.

The type of PC motherboard you have will determine which interface you use. IDE/PATA has been the most popular interface, but it is quickly being replaced by SATA. If you are buying a new motherboard and disk, then SATA is the best choice.

Notebooks or laptop computers use the PCMCIA interface. This interface is used to connect portable devices to the computer. The hard drive is incorporated into the PCMCIA card that plugs directly into one of the notebook’s slots.

PCI is a bus found on many desktop and workstation computers. This bus does not connect directly to a hard drive but it is used to connect one of the other interfaces to the hard drive. For instance, if your motherboard does not support either SATA or SCSI, you could purchase a SATA or SCSI PCI card to provide this hard drive interface on your computer.

The network interface is typically used in corporate environments, but with the spread of Wi-Fi, it is quickly gaining popularity among home and small business users. Computers can boot from a network drive or use a network drive as an auxiliary disk. A home user can take advantage of network storage when he saves his files with an online backup provider.

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