Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!linac!att!ucbvax!ulkyvx.BITNET!rmbult01 From: rmbult01@ulkyvx.BITNET (Robert M. Bultman) Newsgroups: comp.arch Subject: 64-bits, How many years? Message-ID: <9102171510.AA24745@lilac.berkeley.edu> Date: 17 Feb 91 15:10:14 GMT Sender: daemon@ucbvax.BERKELEY.EDU Organization: University of Louisville Lines: 72 In article <6050@mentor.cc.purdue.edu>,hrubin@pop.stat.purdue.edu (Herman Rubin) > In article <3206@crdos1.crd.ge.COM>, davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) writes: > ..................... > > > Assuming that you have a 1 gigaBYTE bus on that memory, it will take > > 316 years (almost 317) to swap a program in. > > The CYBER 205, definitely not the fastest machine in the world, can move > roughly 50 megawords (400 megabytes) per second per pipe. Now even allowing > for overhead (vector units are limited to 65535 words, and setup costs), this > time will not be doubled. I see no way to get your pessimistic result. > -- > And in mccalpin@perelandra.cms.ud el.edu (John D. McCalpin) > Herman probably did not understand what Davidsen was saying. > I get a slightly different number from the following calculation: > > perelandra 1% bc > m=2^64 % number of bytes addressable by 64 bits > 18,446,744,073,709,551,616 % a big number 2*10^19 > r=1,000,000,000 % 1 GB/s data bus rate > m/r > 18,446,744,073 % time in seconds for transfer > m/r/(86400*365) > 584 % time in years for transfer > quit > -- > John D. McCalpin mccalpin@perelandra.cms.udel.edu > Assistant Professor mccalpin@brahms.udel.edu > College of Marine Studies, U. Del. J.MCCALPIN/OMNET Well, here is another slightly different answer: Hypothetical 1 Gbyte transfer rate: =================================== address transfer space rate seconds to years conversion |---------| |---------| |-----------------------------| second hour day year 2**64 bytes X ----------- X ---------- X ------- X -------- = 544.77 years 2**30 bytes 3600 secs. 24 hrs. 365 days Hypothetical slow CYBER 205 operating without setup: ==================================================== address transfer rate 1 seconds to space CYBER 205 pipe years convers. |---------| |-------------| |--------------| second year 1394.61 years 2**64 bytes X --------------- X ---------------- = -------------- 400*2**20 bytes 31,536,000 secs. CYBER 205 pipe Now, just how many pipes are there in a CYBER 205... year define: T = ------------------ 31,536,000 seconds CRAY-1 using all i/o channels at same time: =========================================== 1 word second 2**64 bytes X ------- X ------------------------ X T = 6,093.15 years 8 bytes 500,000 words X 24 chnls (Note: above transfer rate based upon maximum data streaming rate of 500,000 words/second from Richard Russel, "The CRAY-1 Computer System", Communications of the ACM, Jan. '78, V21, N1, Table I, and was assumed to be per channel, not combined) Rob Bultman, University of Louisville, Speed Scientific School