Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!ll-xn!ames!pioneer!lamaster From: lamaster@pioneer.arpa (Hugh LaMaster) Newsgroups: comp.arch Subject: Re: What with these Vector's anyways? Message-ID: <2413@ames.arpa> Date: Tue, 28-Jul-87 14:06:41 EDT Article-I.D.: ames.2413 Posted: Tue Jul 28 14:06:41 1987 Date-Received: Thu, 30-Jul-87 00:40:54 EDT References: <218@astra.necisa.oz> <142700010@tiger.UUCP> Sender: usenet@ames.arpa Reply-To: lamaster@ames.UUCP (Hugh LaMaster) Organization: NASA Ames Research Center, Moffett Field, Calif. Lines: 65 Keywords: vector Cray Cyber CDC Cpu Supercomputers In article <10883@amdahl.amdahl.com> chuck@amdahl.UUCP (Charles Simmons) writes: >In article <2408@ames.arpa> lamaster@ames.UUCP (Hugh LaMaster) writes: >>A vector machine is NOT the same thing as a SUPERCOMPUTER. A supercomputer is >>a loose term generally applied to this year's two or three fastest (usually >>vector) or most expensive (:-) machines. > ... in my experience >the term supercomputer is only applied to extremely fast scalar processors >with attached vector processors. For example, people around here tell >me that an Amdahl 5890 is at least as fast as a Cray (which one?) for >scalar processing. However, a 5890 is "only" a mainframe and not a >supercomputer. I think if you attach a vector processor to a 5890, however, >you do end up with a supercomputer. There are several points here. The first is that "scalar" means several things. To some people it means the speed that that the O/S kernel will run. To others, it means the speed that a small sort, or other "small" data intensive application will run. To others, it means floating point code that is not vectorizable. All of these are different. A subsequent poster mentioned Dhrystone, for example, which is very string intensive and does no floating point; this is not the same "scalar" that a typical Cray user is thinking of ("My Monte-Carlo code runs in scalar..."). When typical supercomputers are touted as good scalar machines, it is with reference to the third version of "scalar" above, not the first. It is worth noting, though, that for many years supercomputers from CDC and Cray were fastest in all three categories. The second point is that there are many other supercomputer designs besides vector machines. A list of them all would be exhausting to read. It so happens that the only really successful machines to date have been vector machines. In the future? A matter of intense debate :-) The third point, is, that I have mentioned previously, vector capability is a cost effective thing to add to minicomputers, and now microcomputers, that are intended for engineering, scientific, and graphics uses. Even though it doesn't make Dhrystone run any faster. It is also worth noting that there are other operations besides floating point that can be vectorized. In particular, bitwise logical operations are useful for image processing/graphics, and encoding/decoding. Vector instructions allow these operations, which can be done in one instruction, and which are thus candidates for a RISC machine, to proceed at (say) one per CPU cycle, on a system where the CPU cycle speed is significantly faster than memory speed (the memory bandwidth on these machines is provided with multiple banks). So, vectorization is not restricted to floating point, and can pay off on even some very simple "one cycle" instructions. Hugh LaMaster, m/s 233-9, UUCP {seismo,topaz,lll-crg,ucbvax}! NASA Ames Research Center ames!pioneer!lamaster Moffett Field, CA 94035 ARPA lamaster@ames-pioneer.arpa Phone: (415)694-6117 ARPA lamaster@pioneer.arc.nasa.gov "IBM will have it soon" (Disclaimer: "All opinions solely the author's responsibility")