Wednesday, July 2, 2008

Difference between a loosely coupled system and a tightly coupled system

What is the difference between a loosely coupled system and a tightly coupled system? Give examples

One feature that is commonly characterizing tightly coupled systems is that they share the clock.
Therefore multiprocessors are typically tightly coupled but distributed workstations on a network are not.
Another difference is that: in a tightly-coupled system, the delay experienced when a message is sent from one computer to another is short, and data rate is high; that is, the number of bits per second that can be transferred is large. In a loosely-coupled system, the opposite is true: the intermachine message delay is large and the data rate is low. For example, two CPU chips on the same printed circuit board and connected by wires etched onto the board are likely to be tightly coupled, whereas two computers connected by a 2400 bit/sec modem over the telephone system are certain to be loosely coupled.

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