Path: utzoo!attcan!uunet!cs.utexas.edu!usc!julius.cs.uiuc.edu!rpi!bu.edu!att!pacbell.com!ucsd!ucbvax!SHUM.HUJI.AC.IL!amos From: amos@SHUM.HUJI.AC.IL (amos shapir) Newsgroups: comp.arch Subject: Re: IBM RS6000 Message-ID: Date: 14 Jan 91 12:55:22 GMT References: <1991Jan10.214122.9506@news.arc.nasa.gov> Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: amos@shum.huji.ac.il Lines: 33 lamaster@pioneer.arc.nasa.gov (Hugh LaMaster) writes: >Scientific researchers are beginning to get results on the IBM RS6000 machines. >(Some RS6000's have apparently been shipping in quantity recently.) >I heard two comments today, which correspond with other things I have heard. >These comments are (beware, hearsay coming): >1) The machines are as fast as other micros on scalar code, and a lot faster > on vector code (other things being equal: clock speed, cache, etc. etc). > Many of the codes here *are* vectorizable. >2) The machine is very, very bad at context switches. So bad, that response > time becomes terrible with *one* CPU bound background process running. It's not heresy any more! I have just run a set of tests comparing the RS6000 to SUN4 an Solbourne workstations. For CPU-bound jobs, it measured about 30MIPS - that depends on how you define MIPS, but the other machines measured 9 and 12 on the same test, respectively. For context-switch bound jobs (running one byte through many pipes) the RS6000 performs about 70% as fast as a SUN4 for up to 8 processes, and up to about 1.5 times faster when more than 8 processes are run. (This "ledge" at 8 processes is a feature of SUNOS, and appears on all Sun hardware). The latter ratio was also reported by the "iocall" (system call overhead) test. The bottom line: it's great for number crunching, but for most interactive jobs it responds as a regular SUN4. -- Amos Shapir amos@shum.huji.ac.il The Hebrew Univ. of Jerusalem, Dept. of Comp. Science. Tel. +972 2 584385 GEO: 35 14 E / 31 46 N city