Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!execu!sequoia!rpp386!jfh From: jfh@rpp386.Dallas.TX.US (John F. Haugh II) Newsgroups: comp.unix.wizards Subject: Cray I/O (was: Re: What kinds of things) Message-ID: <16618@rpp386.Dallas.TX.US> Date: 2 Jun 89 05:28:31 GMT References: <106326@sun.Eng.Sun.COM> <422@ladcgw.ladc.bull.com> <13688@ncoast.ORG> <4609@alvin.mcnc.org> <424@ladcgw.ladc.bull.com> <4616@alvin.mcnc.org> Reply-To: jfh@rpp386.cactus.org (John F. Haugh II) Organization: River Parishes Programming, Plano TX Lines: 28 In article <4616@alvin.mcnc.org> spl@mcnc.org.UUCP (Steve Lamont) writes: >A common criticism heard (and one that I made until I began working on >interactive Crays some three years ago) is that you don't want to be running >vi or emacs on a Cray. The character level interrupts will kill the >poor thing. This is simply not true. They simply do not happen >frequently enough (from the machine's perspective) to worry about. I have also heard that the overhead of sending single character I/O requests over the hyperchannel was extremely costly. The discussion I've read claims that the amount of effort handling single character at a time I/O [ like with Vi ] is too expensive in terms of CPU cycles. There is a posting in one of the sources groups which provides a Vi frontend to ed running on a Cray. I think it had a better description of why Vi is a big loser on a supercomputer. I was also going to disagree with Steve's remark vis memory scheduling by pointing out that the machine has several hundred megawords of physical memory. I think that if you found the ratio between computes [ in MIPS or MFLOPS ] and physical memory, you might discover that compared to a 386PC with 8MB, a Cray is lacking memory. What do you think? -- John F. Haugh II +-Button of the Week Club:------------- VoiceNet: (512) 832-8832 Data: -8835 | "AIX is a three letter word, InterNet: jfh@rpp386.Cactus.Org | and it's BLUE." UucpNet : !bigtex!rpp386!jfh +--------------------------------------