Common internal hard drive interfaces include IDE, SATA, or SCSI. To connect an external hard drive, you’ll probably see USB, eSATA, SCSI, or SAS interfaces.
SATA
SATA stands for Serial AT Attachment. SATA is a common way to connect to storage devices.
SATA Revision 1.0 was the original. It provided speeds ups 1.5 Gbit/s for up to 1 meter.
SATA Revision 2.0 provided 3.0 Gbit/s, for up to 1 meter.
SATA Revision 3.0 provided 6 Gbit/s for up to 1 meter.
SATA Revision 3.2 provides 16 Gbit/s for up to 1 meter.
A SATA drive will generally have a connection for SATA data (7 pins) and another connector for SATA power (15 pins). The SATA data connection connects to the mother board. The larger SATA power connection connects to the power supply.
IDE
IDE stands for Integrated Drive Electronics.
An upgraded version of IDE is called EIDE (Enhanced IDE).
IDE became known to be referred to as PATA. PATA stands for Parallel AT Attachment.
PATA provides 16 MB/s to 133 MB/s speeds. PATA can connect more than just hard drives, it could also connect CD-ROM drives and other peripherals.
PATA cables are ribbon cables with other 40 wires or 80 wires. One end connects to the motherboard and the other end connects to the device drive.
There are two interfaces to connect to the drives. A PATA cable can support 2 drives on a single cable. On a 40 wire cable, device 0 is the interface closest to the motherboard. Device 1 would be the itnterface farthest away from the motherboard. On the 80 wire cable, this is reversed with device 1 being the closest to the motherboard and device 0 being the farthest.
The 80 wire cable is most recent and were designed to support higher throughputs.
On PATA drives, one pin is missing to provide a key so the cable isn’t connected incorrectly. In addition to the PATA data connection, a PATA drive will also have jumpers to set configurations for the drive. A PATA drive will also usually have molex connections for power.
SCSI
SCSI stands for Small Computer Systems Interface. SCSI was originally designed to chain many peripherals together into a single cable/controller. You can have up to 16 devices in a SCSI chain. SCSI has many different formats (Fast SCSI, Ultra SCSI, Ultra Wide SCSI, Ultra2 SCSI, Ultra3 SCSI, Ultra-320 SCSI, Ultra-640 SCSI, iSCSI (SCSI over IP)).
SCSI provides both parallel and serial options.
SCSI connections can not only be used for hard drives, but they can also provide connections for scanners, tape drives, CD-ROM drives, etc.
Minimal configuration was needed to connect devices to a SCSI bus. You’d just assign an ID number to a device connected to the SCSI bus. The SCSI would then automatically handle the communication between the devices on the bus. The SCSI controller is generally assigned to SCSI ID 0. To signal the end of SCSI bus, you use a terminator. This terminator may be built into the last device or there might be an external terminator to connect to the end of the cable.
Serial Attached SCSI
Serial attached SCSI (SAS) devices do not require jumpers, terminators, or configuration of ID information.
SAS moved from parallel to serial communication which increased througput. SAS is a point to point connection which got rid of daisy chaining.
