looi@sutro.SFSU.EDU (W. W. Looi) (02/06/91)
Hi, can someone out there please explain to me what the following mean? - loosely coupled system - tightly coupled system Thanks. -- #include <disclaimer.h> % flame >& /dev/null
wlb@progress.COM (Warren Bare) (02/06/91)
looi@sutro.SFSU.EDU (W. W. Looi) writes: >Hi, can someone out there please explain to me what >the following mean? > - loosely coupled system > - tightly coupled system Well, this really depends on the type of systems you are coupling. Generally tightly coupled systems (whatever they are) know how to communicate with each other very rapidly (i.e. through shared memory) and communicate a large variety of information. For instance, they may know each others state (or have access to it) at all times. Loosely coupled systems, on the other hand, know about each other and can share information with each other but usually though some prespecified communication medium (i.e. ethernet, disk file, pipes, etc ...). They send packets of info that are interpreted by the destination system and acted upon. As a result of this they share much less information. You may actually think of tightly coupled systems as being good friends that know all about each other, and loosely coupled systems as relatives that only talk over the phone. An example of tightly coupled parallel processing is a machine with many CPUs communicating through shared memory (like a Sequent). Loosely coupled parallel processing can be done on a network of Sun workstations. Thanks, Warren --------------------------------------------------------------------- Opinions are my own - not those of Progress Software. Warren L. Bare UUCP: mit-eddie!progress!wlb Progress Software Corp. Internet: wlb@progress.com 5 Oak Park FAX: 1 617 275 4595 Bedford, MA 01730
mpledger@cti1.UUCP (Mark Pledger) (02/07/91)
looi@sutro.SFSU.EDU (W. W. Looi) writes: >Hi, can someone out there please explain to me what >the following mean? > - loosely coupled system > - tightly coupled system Loosely-coupled and tightly-coupled systems refer to the way in which the computer (generally a parallel machine) system memory and/or cpu architectures are designed. A loosely-coupled system has local memory and/or cpu resources as well as globally shared memory and/or cpu's. Where as tightly-coupled systems are isolated from every other memory and/or cpu in the system and they therefore have to talk to each other through a messaging schema. Because the loosely-coupled systems can share memory and/or cpu's, message passing is generally faster. Of course there is the problem of "critical code" to manage the shared memory and/or cpu's. -- Sincerely, Mark Pledger -------------------------------------------------------------------------- CTI | (703) 685-5434 [voice] 2121 Crystal Drive | (703) 685-7022 [fax] Suite 103 | Arlington, VA 22202 | mpledger@cti.com --------------------------------------------------------------------------