[comp.arch] Definition of Fault Tolerant Architectures

ronb@otc.oz (Ron Barrett) (08/11/88)

I'm looking for CONCISE definitions of the following Fault Tolerant 
architectures.
    1) tightly coupled.
  & 2) loosely coupled.

Any help/discussion would be greatly appreciated. Thanks.
-- 
                Ron Barrett
            Network Development
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ACSnet: ronb@otc.oz                     UUCP:   {uunet,mcvax}!otc.oz!ronb

peter@trlsasy.trl.oz (Peter Richardson) (08/12/88)

In article <433@otc.oz> ronb@otc.oz (Ron Barrett) writes:
>I'm looking for CONCISE definitions of the following Fault Tolerant 
>architectures.
>    1) tightly coupled.
>  & 2) loosely coupled.
>
>Any help/discussion would be greatly appreciated. Thanks.

I have found that the following seems to work for most systems:

Loosely Coupled: each processor has its own local memory and IO resources.

Tightly Coupled: processors are not bound to particular memory or IO
	resources (implies high bandwidth interconnections).

To get a more general definition CONCISEness goes out the window.

---
Peter Richardson,			ACSnet: peter@trlsasy.trl.oz 
Telecom Research Laboratories,  	UUCP: {uunet,mcvax}!trlsasy.trl.oz!peter
PO. Box 249, Clayton, Vic. 3168,	Phone: (03) 541-6342
Australia.		        	Fax: (03) 544-2362
D

mark@hubcap.UUCP (Mark Smotherman) (08/16/88)

In article <433@otc.oz>, ronb@otc.oz (Ron Barrett) writes:
> I'm looking for CONCISE definitions of the following Fault Tolerant 
> architectures.
>     1) tightly coupled.

		shared memory, lockstep operation from one clock
		(e.g. FTMP, STAR)

      1A) closely coupled

		shared memory, separate clocks
		(e.g. SIFT, C.mmp)

>   & 2) loosely coupled.

		separate memories, separate clocks
		(e.g. AIPS, ESS)

(Can't find the reference for these distinctions, probably Avizienis or
Siewiorek)
-- 
Mark Smotherman, Comp. Sci. Dept., Clemson University, Clemson, SC 29634
INTERNET: mark@hubcap.clemson.edu    UUCP: gatech!hubcap!mark

Paul_L_Schauble@cup.portal.com (08/17/88)

A system is loosely coupled if it can 'easily' be configured into two syste
running separate programs. Frequently, normal operation of a loosely
coupled system is as two separate systems, one of which can fail without
disrupting the other.

  --PLS