Path: utzoo!attcan2!uunet!husc6!bbn!gatech!hubcap!Chris From: alberta!cdshaw@UCBVAX.BERKELEY.EDU (Chris Shaw) Newsgroups: comp.parallel Subject: Re: parallel numerical algorithms Message-ID: <1796@hubcap.UUCP> Date: 1 Jun 88 20:26:50 GMT Sender: fpst@hubcap.UUCP Lines: 25 Approved: parallel@hubcap.clemson.edu >In article <1691@hubcap.UUCP> you write: >>Anyone care to try for a strict definition? I think that the best way to think of pipelined parallelism under the Flynn taxonomy is to call it MISD. In other words, the "unused" classification among SISD, MISD, SIMD, MIMD does actually contain examples of real machines. I suppose the real difficulty is with definitions: What is an instruction? What is data? What is a CPU? If "instruction" in the Flynn taxonomy means "operate on a data item by passing it from one register through some combinatorial circuit to another register", then the above classification of pipelines as MISD machines makes sense. Of course, assuming that the four Flynn classes are orthogonal is probably a mistake. They can probably best be thought as subsets, where SISD is a subset of MISD, which is a subset of SIMD, which is a subset of MIMD. At the highest level, a Cray X-MP may be MIMD, but each cpu is MISD, while the scalar part of the CPU is SISD. But all this relies on well-defined notions of data, instruction, etc. -- Chris Shaw cdshaw@alberta.UUCP (via watmath, ihnp4 or ubc-vision) University of Alberta CatchPhrase: Bogus as HELL !