Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!lll-lcc!csustan!csun!aeusesef From: aeusesef@csun.UUCP Newsgroups: comp.arch Subject: Re: 64 Vs 32 Message-ID: <589@csun.UUCP> Date: Wed, 25-Mar-87 10:49:04 EST Article-I.D.: csun.589 Posted: Wed Mar 25 10:49:04 1987 Date-Received: Sat, 28-Mar-87 00:39:37 EST References: <3810013@nucsrl.UUCP> <28200016@ccvaxa> <1498@dg_rtp.UUCP> Organization: California State University, Northridge Lines: 50 Summary: I/O processors, large computers In article <1498@dg_rtp.UUCP>, meissner@dg_rtp.UUCP (Michael Meissner) writes: In article <5954@amdahl.UUCP> chuck@amdahl.UUCP (Charles Simmons) writes: > In article <3436@iuvax.UUCP> bobmon@iuvax.UUCP (Che' Flamingo) writes: > >davidsen@kbsvax.steinmetz.UUCP (William E. Davidsen Jr) writes: > >> > >>etc. The 68020 and 80386 have enough power to run large > >>businesses, schools, city and county government, etc. > > Kinda makes you wonder why the Fortune 500 spends on the order of > $5,000,000 for an IBM mainframe or Amdahl mainframe when 68020 > based workstations can be had for on the order of $50,000. While the 68020, 80386 (and whatever the latest 32*32 National makes) are fine in their niches, they are not up to the task of running a moderately large business. Yes the address space is reasonable, but that is not all that goes into making a computer. Ever see a DASD disk farm? (a disk farm is a roomful of large disk drives, and possibly a larger room behind it of cartridges, tapes, etc -- these things store massize amounts of data). The thing that the big guys specialize in is I/O -- with intelligent controllers [channels] offloading the main CPU. I seriously doubt a 68020 workstation could put 100 or so 500M disk drives on it (or if you could, what the response time would be). Data General is a supermini maker, and the largest disk configuration we support is on the order of 15 gigabytes (it may be higher or lower, but that is a ballpark figure). That is a small compared to the large mainframes (it also costs near $1M just for the disks, not to mention the processor needed to support those disks). Well, a good example of what Michael is saying is the pre-180 level Cybers. These are *very* quick machines (a low level one can get something like 3 or 4 MegaFlops), but the CPU does almost no I/O at all. There is, outside the computer, somewhere between 4 and 20 PPU's (Peripheral Processer Units), which are true computers themselves, which handle all of the I/O. All the computer does is put a call in its memory space (usually, probably even always, location 1), and then the PPU sees it, and away it goes. If you need to wait for the data (which you usually do), you force a context switch (save all the registers in a relatively short period of time, load the registers from the last time System allowed a job to run, let it decide what to do), and next time you run, you have your data. Only saving grace on a machine running NOS.... ----- Sean Eric Fagan ------\ Computer Center litvax \ Cal State University, Northridge rdlvax \ 18111 Nordhoff St. psivax --> !csun!aeusesef Northridge, CA 91330 hplabs / AGTLSEF@CALSTATE.BITNET ihnp4 / ------/ "I drank what?!" -- Socrates | My opinions *are* facts