Re: Do we really need virtual machines?

glen herrmannsfeldt <gah@ugcs.caltech.edu>
19 Dec 2004 23:49:43 -0500

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[11 earlier articles]
Re: Do we really need virtual machines? danwang74@gmail.com (Daniel C. Wang) (2004-10-09)
Re: Do we really need virtual machines? gah@ugcs.caltech.edu (glen herrmannsfeldt) (2004-10-09)
Re: Do we really need virtual machines? david.boyle@ed.tadpole.com (2004-10-12)
Re: Do we really need virtual machines? anton@mips.complang.tuwien.ac.at (2004-10-17)
Re: Do we really need virtual machines? Colin_Paul_Gloster@ACM.org (Paul Colin Gloster) (2004-10-21)
Re: Do we really need virtual machines? postmaster@paul.washington.dc.us (Paul Robinson) (2004-12-17)
Re: Do we really need virtual machines? gah@ugcs.caltech.edu (glen herrmannsfeldt) (2004-12-19)
Re: Do we really need virtual machines? tobias@berg.dichter.de (Tobias Bergmann) (2004-12-22)
Re: Do we really need virtual machines? vbdis@aol.com (2004-12-23)
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From: glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups: comp.compilers
Date: 19 Dec 2004 23:49:43 -0500
Organization: Comcast Online
References: 04-10-013 04-12-081
Keywords: VM
Posted-Date: 19 Dec 2004 23:49:43 EST

Paul Robinson wrote:


(snip)


> I'm not sure if that is what has been claimed, or if that's your opinion
> but if it is what is being claimed, it's obviously dead wrong.


> A Virtual Machine solves one problem and only one: allowing a
> particular binary program to be operated in a non-compatible
> environment. That the environment may not exist anywhere except in
> software isn't really relevant.


I would say that in addition they can provide more debugging
facilities than the hardware normally provides.


IBM used CP/67 to develop S/370 software before enough machines were
available, and VM/370 to help in debugging after they were available.
IBM's VM has kept the ability to run itself, I would presume, for
debugging purposes.


I am not so sure that JVM provides debugging facilities similar to
VM/ESA, but it could be done much easier than adding debugging
features to the hardware.


-- glen

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