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From: gelfand@valid.UUCP (Brooks Gelfand)
Newsgroups: net.followup
Subject: Re: FYI: VM systems on the net
Message-ID: <455@valid.UUCP>
Date: Thu, 17-Jul-86 15:08:20 EDT
Article-I.D.: valid.455
Posted: Thu Jul 17 15:08:20 1986
Date-Received: Fri, 18-Jul-86 04:45:32 EDT
References: <6340MW9@PSUVM> <-121460420@sysvis>
Organization: Valid Logic, San Jose, CA
Lines: 47

> 
> > I would just like to take this opportunity to inform people that there are
> > VM systems on the net now.  We've been on for awhile and would now like to
> > be considered in discussions.  UN*X doesn't rule the world.  In fact, it
> 
> I heard that VM stands for Visceral Maggots.  True?  It's uncommon for an
> "OS" to SUCK down about 40% of the total available machine cycles for overhead,
> as does VM.  That's why it wasn't tagged with an `OS' label, I'm sure.   Who
> needs VM?   Who cares?   IBM didn't have an official `C' compiler as of some
> time ago so what are you going to do with sources that won't compile, and if
> they did, the I/O is handled totally differently?   Batch is bitch, Butch.
> Try net.jokes instead of net.sources for your jollies.  If VM is so great, why
> aren't all the "good" microcomputers  [IBM/AT (-:]  using it?
> 
>     "VM is to operating environments as barnacles are to ships."  -me

Oh boy, sounds like we have a REAL COMPUTER SCIENTIST here.
Having used both VM and UNIX I'd like to add my opinions.
First -me is a bit behind times. VM use to take about 40% of the machine cycles
on the old 370/145 about 12 years ago. Since then, the addition of microcode
assists has reduced the overhead to about 10%. However, depending on the
guest operating system, this overhead may be offset by the 
increased efficiencies in CCW translation (what the machine does to 
perform an I/O) and storage management. As to who needs VM and who cares -
the people who are running it, that's who. There are many VM sites.
As to the 'OS' label, VM is more than an operating system. When a user
logs on under VM, rather than just being a process each user thinks 
he has his own 370 complete with control registers, general registers,
PSW, memory and I/O devices as allocated in the directory. Thus you
have your own Virtual MACHINE - hence the name VM. In this machine
you IPL (boot) whatever operating system (OS) you want (and have
access to) e.g. CMS, MVS, DOS/VSE, UNIX. You don't like these?
There is a good assembler with CMS; write your own. The advantages of this
system are obvious. If a program in one virtual MAchine does something
that would crash the machine, only that virtual machine goes down. The
other users continue to operate. The only effect they see is a slight
increase in speed, since the crashed 'machine' is not using any cycles.
Since VM handles all the I/O, it is an excellent system for people who
who are debugging Physical IOCS. Vm will not let the user move the 
disk heads outside their alloted area even with PIOCS. Thus one user
cannot corrupt anothers files by accident  or even on purpose.

Last but not least, VM will run on both the PC/XT370 and the PC/AT370.
It runs slowly but it runs. 

Brooks Gelfand
...!hplabs!pesnta!valid!gelfand