Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!snorkelwacker!apple!mips!winchester!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.arch Subject: Re: Extremely Fast Filesystems Message-ID: <40714@mips.mips.COM> Date: 9 Aug 90 02:50:36 GMT References: <5539@darkstar.ucsc.edu> <13285@yunexus.YorkU.CA> <30728@super.ORG> <13667@cbmvax.commodore.com> <40644@mips.mips.COM> Sender: news@mips.COM Reply-To: mash@mips.COM (John Mashey) Organization: MIPS Computer Systems, Inc. Lines: 102 In article wayne@dsndata.uucp (Wayne Schlitt) writes: >> Well, there are always less higher-end things than lower-end ones. >> However, I'd STRONGLY disagree with the idea that 64-bit machines will >> remain confined to the super- & minisuper world for 10-20 more years. ^^^^^ >yes, 20 years is probably too long but i think that 10 years isnt too >far off the mark. my guess is that it will be 7-10 years before 64bit >computers are making inroads into the 32bit market. (maybe by then we >will have finally gotten away from 16bit computers. 1/2 :-) Well, 7 isn't too far from 5. >> I propose instead: >> a) We are currently consuming address space at the rate of 1 bit year. >i thought it was only 1 bit per 18 months... new data? Rough rule in any case. Hennessy&Patterson claim (page 16): "This translates to a consumption of address bits at a rate of 1/2 bit to 1 bit per year." Hennessy always says informally, that the old rule of 1/2 bit per year has tended to shift more towards 1 bit per year with MOS memories. In any case, this is a vague enough metric that these are in the same ballpark. :-) > >> b) [says that there are commercial people who already want >> 31-32 bits of virtual address space, and they want more.] >and they are putting these applications on everyone's desk...? or are >these applications things that they would have run on mainframes or >super-mini's if your "killer-micro's" werent chosen? Well, the one's I've heard of weren't for everybody's desk, but they would have liked them to be on some people's desks, and were running on architectures suitable for the desktop. > >> c) Observe that there already exist desktop workstations that >> support max physical memories in the 128MB - 512MB range, >> using 4Mb DRAMs. Hence, by the 64Mb DRAM generation, one can expect >> 2GB - 8GB maxes. After all, at that point, you can get 4GB or >> so within a 1-ft cube. >using your own numbers, at one bit a year it will be 3-5 years before >physical memory _maximums_ will reach 4GB. at one bit every 1.5 >years, it will be more like 4.5-7.5 years. how long do you think it >will be before 4GB is typical? Well, I don't think 4GB/desktop will be "typical" for a long time, if ever. I do think that there will be reasonable numbers of machines whose maximum memories are in this range, for a whole bunch of the typical reasons that cause systems to be built in certain ways. a) Note that the "bit/year" rule is really applicable to virtual memory, not necessarily physical memory, although the latter certainly correlate with the former. (Old saw: virtual memory is a way of selling more physical memory.) b) Anyone building a system will typically design it for at least 2 generations of DRAMS. Right now, at least DEC, MIPS, and Sun build desktops that use either 1Mb or 4Mb chips to cover various ranges. I'm sure most everybody else does, also. > >also, when do you expect 64Mb DRAMS to come out? my guess would be >around 5-6 years or so, and then it will take at least a year before >they have ramped up production to the point that they are cheaper than >16Mb DRAMS. (as a reference point, would you consider 4Mb DRAMS >"common" now? when do you think that 4Mb DRAMS became or will become >"common"?) I'd consider 4MB DRAMs "common" (not "prevalent"): multiple vendors have been delivering them in desktop systems already. (Some of the very first MIPS Magnums that got sold had 128MB maxed-out memories in them :-) Suppose you get 16Mb chips in the same state in 1993-1994, and 64Mb chips in 1996-1997, or 1995 if you're really lucky. Certainly, people who design systems tend to allow for at least 2 DRAM sizes in boards, so things designed 1 year before 64MB chips become practical will allow for them. All of this says that a Magnum-like design appearing in 1995, would like come out the door to use 16Mb chips, which would give a max memory of 512MB, and then upgrade to 2GB max. A DECstation5100-like design has space for 4X more memory. Again, I make no claims that such would be "typical" (whatever that is). However, people like to buy systems whose max memories are bigger than typical to leave them room for growth. Application areas that will tend to want this stuff quickly include: ECAD, MCAD, Image applications, geographic information systems, financial modeling, as well as databases. Observe that large memories are one of the few obvious helps for DBMS read-performance assistance, so you'll see it in the commercial world, as well. (back to virtual-address space) Finally, all of the economics of the business say that people like to have ranges of machines that can run the same software. It may well be that you may well have servers that have massive amounts of memory (sorry, lots of people WILL have servers with massive amounts of memory), and smaller desktop/desksides, but you'd certainly like to run the same applications on both at least some of the time, even if you back up the desktop with less physical memory. Again that's why I'd claim that 1995-micros will want to either be 64-bit ones, or least have 64-bit modes. Note that with the number of tranisistors likely to be available, you can probably stuff a 32-bit CPU in the corner of your 64-bit one to handle backward compatibility. -- -john mashey DISCLAIMER: UUCP: mash@mips.com OR {ames,decwrl,prls,pyramid}!mips!mash DDD: 408-524-7015, 524-8253 or (main number) 408-720-1700 USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086