[rescue] More IBM emulation fun
mrbill at mrbill.net
Tue Feb 10 01:15:49 CST 2009
On Mon, Feb 09, 2009 at 11:08:00PM -0700, Scott M wrote:
> At this URL, this doc: Introduction_To_VM370_Course_Jul75.pdf
> has this chapter heading: "VIRTUAL MACHINE DESCRIPTION".
> Virtualization in 1975? Really?
"The pioneer system using this concept was IBM's CP-40, the first (1967)
version of IBM's CP/CMS (1967-1972) and the precursor to IBM's VM family
(1972-present). With the VM architecture, most users run a relatively
simple interactive computing single-user operating system, CMS, as a
"guest" on top of the VM control program (VM-CP). This approach kept the
CMS design simple, as if it were running alone; the control program quietly
provides multitasking and resource management services "behind the scenes".
In addition to CMS, VM users can run any of the other IBM operating
systems, such as MVS or z/OS. z/VM is the current version of VM, and is
used to support hundreds or thousands of virtual machines on a given
mainframe. Some installations use Linux for zSeries to run Web servers,
where Linux runs as the operating system within many virtual machines.
Full virtualization is particularly helpful in operating system
development, when experimental new code can be run at the same time as
older, more stable, versions, each in a separate virtual machine. The
process can even be recursive: IBM debugged new versions of its virtual
machine operating system, VM, in a virtual machine running under an older
version of VM, and even used this technique to simulate new hardware."
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