wasser_1@viking.DEC (John A. Wasser) (04/05/85)
> Path: decwrl!decvax!genrad!panda!talcott!harvard!seismo!ut-sally!ut-ngp!utep-vaxa!bryan > Posted: Tue Apr 2 14:15:22 1985 > > Is it ever possible to run out of Virtual Memory? > > "Welcome to the machine." Bryan R. Davies > (Pink Floyd) ihnp4!ut-sally!utep!bryan Of course it is possible to run out of Virtual Memory if by "run out" you mean "having no more space in which to store things". Virtual Memory is just a way of mapping a large (but finite) ammount of mass storage into the processor address space. Of course it is not possible to run out of Virtual Memory if by "run out of" you mean "execute directly instructions stored in". Your program has to be loaded into physical memory before it can be executed. I hope this covers both of the answers. -John A. Wasser Work address: ARPAnet: WASSER%VIKING.DEC@decwrl.ARPA Usenet: {allegra,Shasta,decvax}!decwrl!dec-rhea!dec-viking!wasser Easynet: VIKING::WASSER Telephone: (617)486-2505 USPS: Digital Equipment Corp. Mail stop: LJO2/E4 30 Porter Rd Littleton, MA 01460
45223wc@ahuta.UUCP (w.cambre) (04/08/85)
REFERENCES: <1515@decwrl.UUCP> In theory, no you can't run out of virtual memory. But computer systems limit how much of it you can address. For example IBM's MVS pre-XA uses 24 bit addressing so you can only use up to 16Mb of virtual memory. Which by the way, is not enough for some of our users. That's why we are going to MVS/XA and 31 bit addressing.
ndiamond@watdaisy.UUCP (Norman Diamond) (04/09/85)
> In theory, no you can't run out of virtual memory.
Because theoretically, there's no limit on the size of a virtual address
that you can put in an instruction? It's going to take you an awfully
long time to write that code, or for a compiler to generate the object
code.
--
Norman Diamond
UUCP: {decvax|utzoo|ihnp4|allegra}!watmath!watdaisy!ndiamond
CSNET: ndiamond%watdaisy@waterloo.csnet
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"Opinions are those of the keyboard, and do not reflect on me or higher-ups."roy@phri.UUCP (Roy Smith) (04/16/85)
> [...] But computer > systems limit how much of it you can address. For example IBM's > MVS pre-XA uses 24 bit addressing so you can only use up to 16Mb > of virtual memory. Which by the way, is not enough for some of our > users. [...] I'm not sure why this is in net.puzzle, so I'm followup-to'ing it to net.arch, and cross-posting this there. I remember reading once that the biggest address size you would ever need would be 200 bits. The reason for this is that there are 2**200 atoms in the universe and it is absurd to want to enumerate more things than that. Any comments? BTW, Offhand I can already think of things like sparse hash tables which might fly in the face of this argument. -- cmcl2!rocky2!cubsvax -\ vax135!timeinc -> !phri!roy (Roy Smith, System Administrator) allegra -/ The opinions expressed herein do not necessarily reflect the views of the Public Health Research Institute.