Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!ncar!boulder!sunybcs!bingvaxu!leah!itsgw!steinmetz!uunet!sco!seanf From: seanf@sco.COM (Sean Fagan) Newsgroups: comp.os.misc Subject: Re: character-at-a-time I/O (was Re: Re^2: Unix bigotry) Message-ID: <2317@scolex.sco.COM> Date: 20 Feb 89 21:56:09 GMT References: <4434@freja.diku.dk> <5900004@hpfcdc.HP.COM> <3472@sugar.uu.net> Reply-To: seanf@scolex.UUCP (Sean Fagan) Organization: The Santa Cruz Operation, Inc. Lines: 87 In article <3472@sugar.uu.net> karl@sugar.uu.net (Karl Lehenbauer) writes: >In article <5900004@hpfcdc.HP.COM>, marc@hpfcdc.HP.COM (Marc 'Sphere' Sabatella) writes: >> ...and >> the numerous kludges necessary to get Unix to run on a machine with 60 bit >> words is also bound to slow it down a little more, etc. >64-bit words. 60-bit, ones-complement, 6600 emulation is thoughtfully >provided for sites for whom converting their software is an overwhelming >task. For example, every PLATO site in the universe. *sigh* 170-state machines have 60-bit words. 180-state machines, some of which can emulate 170-state machines, have 64-bit machines. The 170-state emulation by the 180-state machines is, by the way, 7600 + CMU (Character Move Unit), not 6600. And, joy of joys, 180-state is 2's complement, not 1. Frightening. >I have a theory that for a lot of sites, mainframes are not a win. Consider >that if you're sharing a mainframe among too many people, you may not be >getting as many CPU cycles overall as you would if you had your own workstation >(The mainframe guy willing to come in at midnight gets a lot of cycles, though) CPU cycles aren't everything, though. If it were, noone would be running UNIX, since it steals too many cycles away with all of its foolish context switches and multitasking. >So it comes to a question of how many cycles are you getting, are you getting >enough (never), and what can you do with them. I contend that, although it >is possible to get a lot of cycles from a mainframe, you don't always, and >when you do, you can't always use them in the ways you intend, as shown by >the fact that you can't do character-at-a-time I/O under a lot of mainframe >OSes, and mainframes have rotten timesharing environments in general. > >Another thing, mainframes are harder to program. At least, historically, user- >friendly software came from minis and PCs. Uhm, where did you get this idea? PLATO, which is very user-friendly, was written for Cybers, some of which, I will agree, are minis. >And finally, there is *the challenge* to mainframes. How much (in scalar MIPS) >faster is a Cyber 20x than a fast MIPS M2000 like the DECstation 3100? Just a >few times, right, like less than ten? A Cyber costs several dozen times more, >right? (Granted, I/O and vector MFLOPS are another consideration, although >there are some promising chip developments in this area, too, such as smart >boards and fast buses for the former and the Intel N10 and Weitek chips for >the latter.) I'd rather have 15 MIPS waiting on my 'enter' key (and doing other >stuff, of course) than submit a batch job for 1/20th of 100 MIPS, not to say >*some* people don't need them, just that a great many do not. A Cyber 170/760 will, for the most part, out perform most applications under Unix on a VAX, any model. Why? Because of the I/O. It doesn't have vectors, and only gets 10MIPS/MFLOPS. However, when you work in the *throughput* it gets, it becomes a *very* large win. Also, since you don't mind having a 15MIPS machine waiting for you enter key, how are you going to feel when, if you have a uucp connection, or an ethernet connection, it starts to slow down to an effective 8 MIPS or so during large transfers? How do you feel about the 15MIPS being idle most of the time? I can buy a DEC MIPS 3100 machine for about 12k. This will get me something like 10 MIPS or so. I can also get a CDC Cyber 180/830 for 100k. This will get me something like 3 MIPS or so. (Neither price represents any sort of discount). If I'm in any sort of business, the Cyber is going to be a better buy, since I can put 20 people on it without slowing down much. The DEC machine will become unacceptably slow if I put 20 people on it, all doing FORTRAN compiles. Or, I suppose, I could buy 20 DEC's, for a total of something like 240k. Even with just one user, I'll still lay odds that the Cyber (running NOS or NOS/VE) will be able to compile SPICE faster than the DEC machine. >I'm not a luddite or anything, though, which is to say that I would not mind >having 100 MIPS waiting on my 'enter' key ;-) So you enjoy paying extra thousands of dollars for something you don't use, right? People who buy Cray's, Cyber 205's, and ETA's *don't*, and there are times when they need every CPU cycle they can get, for upwards of 10-30 large, intensive applications. Don't run it under Unix (well, on an ETA, you might get a shot of some real speed, especially if they ever port Mach to the blasted thing). I wouldn't even suggest running it under NOS/VE. For a personal computer, Unix (and single-character I/O) is fine. For a mini, its debatable (Unix is ok, there, but I'd rather let some board handle the I/O than interrupt the CPU), and for mainframes and supers, try some other approach first. -- Sean Eric Fagan | "What the caterpillar calls the end of the world, seanf@sco.UUCP | the master calls a butterfly." -- Richard Bach (408) 458-1422 | Any opinions expressed are my own, not my employers'.