Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!spool.mu.edu!uunet!bywater!arnor!arnor!marc From: marc@watson.ibm.com (Marc Auslander) Newsgroups: comp.arch Subject: Re: Fast I/O Message-ID: Date: 21 May 91 13:12:26 GMT Article-I.D.: marc.MARC.91May21081226 References: <97b302n807vo01@JUTS.ccc.amdahl.com> <13096@pt.cs.cmu.edu> Sender: news@watson.ibm.com (NNTP News Poster) Organization: IBM T.J. Watson Research Center, Hawthorne, New York Lines: 12 In-Reply-To: wayne@dsndata.uucp's message of 20 May 91 01:18:10 GMT Nntp-Posting-Host: marc The old System 370 rule of thumb for I/O capacity was 1 instruction per BIT of I/O. The ratio is called (at least in IBM) E/B, spoken "E over B". Less than one was I/O intensive, greater than one cpu intensive. A risc workstation running a real 10 mips today might be capable of 100 4k disk transfers a second, which is about 3 megabits. So E/B is about 3. In other words, by the old standards, workstations are optimized for computation - which is in fact correct. -- Marc Auslander