Small Computer Systems Interface – SCSI

SCSI, or Small Computer Systems Interface, also pronounced “scuzzy” is defined as a standard type of input and output system used to attach peripheral devices to provide a very fast connection rate. These devices can be scanners, hard disks or other devices that can connect to a computer. Most Mac computers and operating systems use SCSI connections and they come in a several varieties.

The purpose of using SCSI connections is that the transfer rate is much faster than parallel ports. Data can be transferred up to 160 megabytes per second than standard serial and parallel ports. Also, many devices can be attached to a SCSI port.

The SCSI ports are most commonly used for peripheral devices such as hard disks, tape storage devices and printers. CD ROM drives, CD burners and recorders and DVD drives are also able to connect to SCSI ports. Even SCSI compatible printers can be purchased and compatible with the SCSI system. Most devices that are compatible with SCSI will have a built in terminator that can either be enabled or disabled. If the device does not have an active terminator already built in, one can be purchased. There are several varieties of SCSI cables available because the SCSI system is so flexible.

There are many benefits to using SCSI. SCSI provides a high-speed, intelligent interfacing that can allow for up to 16 different peripheral connections on a single bus. The faster the SCSI transfer rate, the faster the data and information is available to the user. The SCSI is also very reliable and it works on most computer systems.

The problems with SCSI are few. One potential problem is when using SCSI, it must be configured for a specific computer. The SCSI also has limited BIOS support and there is no common software interface. Another potential problem while using SCSI is that it has many variations that can be confusing to a new user.

There are three basic types of SCSI. The SCSI-1 was the first type of SCSI that was developed in 1986. The SCSI-2 was the second variation that was became a standard in 1994. The key component to SCSI-2 was the inclusion of the CCS (Common Command Set). These are the 18 commands considered to be necessary to make any SCSI device run smoothly. Also included in the SCSI-2 is the command queuing which allowed that any SCSI device to store a series of commands from the host computer. This queuing determines which commands are given first priority.

The third variation of SCSI is the SCSI-3, which came soon after the second variation in 1995. This variation can sometimes be confusing to the new user. This variation is not considered the standard since it has smaller built-in standards than the SCSI-2. The SCSI-3 uses other variations including Ultra, Ultra2, and Ultra3. The fast and wide designations work like the SCSI-2 and the fast designation means that the speed has been doubled. The SCSI-3 can add functionality and performance improvements to the system in use. The SCSI-3 also uses glass fiber optic cables instead of traditional ribbon cable connections.

There are three main parts of any SCSI system. These include the controller or host adapter, the device and the cable. The controller is the main part of the SCSI system. It serves as an interface between any devices connected to the unit. The controller might be a built into the motherboard device or it might be a card that can be plugged in to the computer. The controller also contains the BIOS, which is the ROM or software memory chip that controls devices hooked into the SCSI. Most devices that are connected with the SCSI have a built in adapter that allows the unit to communicate. These devices are called embedded SCSI devices.

Another thing to remember when looking at SCSI is that SCSI is not the same as SASI, which was developed in the 70s. SASI was originally designed to work with disk drives only. SASI also operated much slower at 1.5 MB second than the newer SCSI. The older version of SCSI-1 was based on the SASI system making the SASI system obsolete. The two systems cannot be used together.