The SCSI standard is no longer common in consumer hardware devices, but you’ll still find it used in some business and enterprise server environments. More recent versions include USB Attached SCSI (UAS) and Serial Attached SCSI (SAS). Most computer manufacturers have stopped using onboard SCSI completely and use much more popular standards like USB and FireWire for connecting external devices to computers. USB is much faster, with a maximum incoming speed approaching 40 Gbps. SCSI is based on an older interface developed by floppy disk drive manufacturer Shugart Associates and called Shugart Associates System Interface (SASI), which later evolved into Small Computer System Interface, abbreviated as SCSI and pronounced “scuzzy.”
How Does SCSI Work?
SCSI interfaces used internally in computers to connect different types of hardware devices directly to a motherboard or storage controller card. When used internally, devices are attached through a ribbon cable. External connections are also common and typically connect via an external port on a storage controller card using a cable. Within the controller is a memory chip that holds the SCSI BIOS, which is a piece of integrated software that’s used to control the connected devices.
What Are the Different SCSI Technologies?
There are several SCSI technologies that support different cable lengths, speeds, and a number of devices that can be attached to one cable. They are sometimes referred to by their bus bandwidth in MBps. Debuting in 1986, the first version of SCSI supported eight devices with a maximum transfer speed of 5 MBps and a maximum cable length of six meters. Faster versions came later with support for 16 devices and a 12-meter maximum cable length. Here are some of the other SCSI interfaces that have existed:
Fast SCSI: 10 MBps; connects eight devicesFast Wide SCSI: 20 MBps; connects 16 devicesUltra Wide SCSI: 40 MBps; connects 16 devicesUltra2 Wide SCSI: 80 MBps; connects 16 devicesUltra3 SCSI: 160 MBps; connects 16 devicesUltra-320 SCSI: 320 MBps; connects 16 devicesUltra-640 SCSI: 640 MBps; connects 16 devices
