Newsgroups: comp.parallel.pvm
From: pdinda@cs.cmu.edu (Peter A Dinda)
Subject: Re: PVM on Windows PCs?
Organization: School of Computer Science, Carnegie Mellon
Date: 26 Aug 1994 11:34:14 GMT
Message-ID: <33kjvm$pjc@cantaloupe.srv.cs.cmu.edu>

In article <33jadr$gbo@falcon.ccs.uwo.ca>,
Crispin Cowan <crispin@csd.uwo.ca> wrote:
>	-it will suck (lack of true multitasking)

I'm not sure how you define "suck."  Depending on how it was
implemented, it should be possible to produce better bandwidth and
latency than under a Unix operating system for the simple fact that
hardware can be directly manipulated under Windows.  As for the
"lack of 'true' multitasking" - note that Windows has two levels of
scheduling.  At the lowest level, pseudo-virtual machines are 
preemptively scheduled.  These include DOS VMs that can run DPMI
DOS (32 bit linear addressing with use of 32 bit datapath) applications.
One of the VMs runs the Windows environment that we see.  WITHIN that
VM, multiple Windows applications are cooperatively scheduled via a
single event queue and no preemption.

>	-it will be unsafe (lack of inter-process protection)

"lack" is the wrong word.  "weak" is more accurate.

>	-it will be a lot of work (to cobble together compatible
>	 interfaces for signals, rsh, etc.)

This has been done for other platforms:  Paragon, T3D, etc.

>	-it will have portability problems (if compromises are made to
>	 help with the previous points, such as mandating calls to
>	 yield--ick)
>
>PVM emulates the functionality of an MPP environment by emulating the
>MPP facilities using UNIX facilities.  Windows is neither of these

Again, this is true for PVM running on workstations.  It's certainly
not the case for PVM running on a Paragon, T3D or under OS/2.  

>environments, and isn't even really an operating system, so it will

That's a poser.



