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SubjectRe: Linux for JavaVM
On Tue, 07 Jan 97 22:00:17 +1000, wrote:

> Running Linux in Linux in Linux would be a great thing! I've been reading
>reports about how IBM's older mainframes worked and specifically about the
>architecture of VM/DOS. Apparently they had a virtual machine which the OS ran
>in, the VM provided file access and linear memory to the OS.
I did a lot of work on that system, called VM. There was a control
program (CP) which ran virtual machines. It was all written in S/370
assembler and was about 300K lines of code (VM and the user interface
called CMS which had a file system, an exec language, and little else).
Of course that excludes compilers, etc.

Most of the work was a detailed simulation of memory and I/O. S/370 I/O
is complex, involving channel programs (you don't want to know). It also
simulated privileged instructions. The result was sufficient to run VM
under VM, which was a marvelous development environment. Imagine single
stepping, breakpointing, etc at the kernel level.

A big project to duplicate. Incidently, VM still exists and is being
enhanced even today.

john alvord

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