My husband and I celebrated out 20th wedding anniversary this past summer. Twenty years ago we had a short courtship prior to our marriage. We played tennis, took walks and ate dinner together between July and October and after 2-3 months it was clear that we wanted to spend the rest of our lives together.
Human relationships are complex, but one thing that is certainly true in my relationship with my husband is that we are compatible. Our lives have changed a lot over the past 20 years. We have finished school, moved to a new community and now have two children. Despite these major external changes, we have continued to live in harmony with each other.
Compatibility is equally crucial in the harmonious relationships of computers.
The Central Processing Unit (CPU) or the mainboard of your Personal Computer (PC) would be useless without the common parts that attach to it. Quite obviously your CPU must have an attachment to an input source like a keyboard and an output source like a monitor.
For example, my office computer is made by FLEX, my monitor by Panasonic and my keyboard by Sejun Electron, Inc. in China. Despite the fact that they were made by different companies in different countries they must be compatible if they are to move data to and from each other.
Even within the main housing of my FLEX PC there are multiple components that must be compatible. My internal modem, CD ROM drive and Floppy drive must have a communication pathway to the main board and must move bits of data back and forth in a way that is compatible.
Unlike my husband and I who have been able to adapt to our changing lives and aging bodies and still remain compatible, computers are generally inflexible.
To address the need for compatibility in a modular environment, the computer industry has set standards for the connections between certain components. One example of a standard that creates compatibility is SCSI.
In the early 1980’s when Personal Computers were just coming into common use many of the components of the computer were external to the main computer housing. Main boards and other electronic components were larger, so space inside the main computer case was limited. Many of the familiar computer components such as floppy drives, hard drives and modems were external or out of the main housing.
In 1981 the Shugart Associates System Interface (SASI or “sassy”) began to be used as a specific interface for the main board of the PC to interact with these external peripherals. SASI was a proprietary BUS or pathway that allowed a compatible exchange of bits of data between the main board and the peripherals.
In 1986 the American National Standards Institute (ANSI) accepted SASI as an industry standard interface between a PC and its peripherals. Once this proprietary interface became a standard it was renamed Small Computer System Interface (SCSI or “scuzzy”).
For the main board of a computer to connect to a component through SCSI there is a physical connection. For components that are still external to the main computer housing this connection is through a round cable that has a flat plug-in connector with pins at either end.
Some peripherals now can be plugged in through SCSI inside the main computer housing. The internal physical SCSI connector is a flat ribbon cable.
SCSI moves data between the main board of the computer and the peripherals in a standard or protocol fashion. This protocol is not dependent on the type of device that is being connected. SCSI is described as “intelligent” because it can connect up to 16 devices to the main board. With its “plug and play” feature SCSI will automatically recognize the devices such as printers, scanners, hard drives it is connected to and assign them ID numbers that can be recognized by the main board.
SCSI is high speed. The original SCSI in 1986 was SCSI-1. It had a “BUS width” of 8 bits which means that it could process 8 bits of data in a cycle. SCSI-1 had a clock speed or cycle speed of 5 Megahertz (5 million cycles per second).
SCSI-2 became the standard in 1994 and among its advantages were a BUS width of up to 16 bits and/or a clock speed of 10 MHz.
Today Ultra3SCSI is in use for some connections, but it has not yet been accepted as an industry standard. With a BUS width of 16 bits and a clock speed of 40 MHz it is very fast.
So, data travels between the main board and the peripherals in a fast, reliable and intelligent manner through the Small Computer Systems Interface AND SCSI is widely compatible among IBM, IBM clones, Macintosh and UNIX-based main boards with many peripheral devices.
My husband and I look back on the day we first played tennis together and feel we knew from that moment that we were perfectly compatible, but it is interesting that he cannot imagine anyone to be compatible with our teenage daughter.
I can see him now standing at the dining room window on a Saturday night watching a poor unsuspecting peripheral pull up in our driveway, park and ease out of the car. Frank will walk to the bottom of the stairs, put both hands on his hips and call upstairs to his only girl-child, “SCSI, definitely scuzzy. Sawim‘ Comin’, Strikingly Incompatible. Don’t worry, I’ll put him on the Ultra-fast 16 bit BUS one way….OUT!”
If our daughter ever really wants to go out on a date and ever make any connection, then she probable should start working today on standards to be submitted to DAD…Do-not-ever Allow Dates.
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