Types of Hard Drive Interfaces
The topic of hard drive interfaces, as of 2009, is split into two sub categories. Internal hard drive interfaces include the EIDE and SATA standard, while the external hard drive market is split between the USB, FireWire, and eSATA specifications. Though these standards vary widely in their appearance and design architecture, they are easy to implement and understand.
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Internal EIDE Specification
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The EIDE, Enhanced Integrated Drive Electronics, specification was set forth by the Western Digital Corporation in 1986 as a successor to the AT drive interface. EIDE uses a 40-pin male connector on the drive itself that is connected to a 40 or 80 wire ribbon cable. This cable connects to an EIDE interface on the system's motherboard that is capable of supporting two devices per channel. EIDE is capable of transfer speeds ranging from 16 MB/s to 133 MB/s.
Internal SATA Specification
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The SATA, Serial ATA, specification was released in 2003 as a successor to the EIDE interface for hard drives and optical drives. The SATA hard drive interface consists of a seven-pin data cable, which connects the drive to the system motherboard. SATA hard drives are capable of speeds of 1.5, 3.0 and 6.0 Gbit/s. The SATA specification allows for "Hot Swapping" that enables, drives, under specific hardware configurations, to be removed and installed into a system without the need for a system shutdown.
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External USB Interface
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USB, Universal Serial Bus, is the current 2009 industry standard for all peripheral connectivity with computer systems. USB connectors come in two flavors, six pin standard size and four pin miniature versions for connectivity with laptops and small electronics such as MP3 players. The USB standard is currently in its second revision known as USB 2.0 and supports plug and play connectivity with maximum transfer speeds of up to 480 MB/s.
External FireWire Interface
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FireWire, also known as IEEE 1394, is the market competitor to USB. FireWire uses a serial bus interface for high speed transfers between devices and computers. The maximum transfer speeds attainable with FireWire range between 50 and 400 MB/s depending on the specifications of the device using the interface. FireWire generally transfers data faster than USB devices as they require more low level processing from devices for data transfer. Further, FireWire allows for peer to peer communication between devices and as such requires less computing resources to transfer between devices.
eSATA Interface
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ESATA, external SATA, is a specification set forth in 2004 for use with external data devices. Though USB and FireWire dominated the external drive industry at the time, eSATA realized that most external hard drives were merely EIDE hard drives with a converter to make them able to connect with USB or FireWire ports. ESATA allows for SATA drives to be connected externally with the same speeds as an internal SATA hard drive. ESATA enjoys the same transfer speeds of its internal counterparts with cable lengths of up to 1 meter.
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