[Simh] Regarding "Cutler THE father of VMS" myth

[Clem Cole]

On Wed, Mar 4, 2015 at 6:22 PM, Sergey Oboguev <oboguev at yahoo.com> wrote:

> > Unix has been able to embrace the ideas easily and I do not think
> > that would have been easy with VMS
>
> It would not, which makes it even more curious that there was a pilot
> effort at reimplementation of VMS on top of Mach.


​Sorry, my wording was not as crisp as it should have been.   Indeed,
re-implementing VMS on top of uKernel is possible and was
proposed/attempt/done at least twice - in fact I was part of one of them
(I.e. I know of 2 projects that actually started and a 3rd that proposed
it, there may have been more).  But in all three cases, they took or
planned to use a uKernel, with a more standard supervisor/user mode scheme
and then implemented the VMS APIs and services on top of it; then
reimplement a number of the VMS commands [since parts of the command system
was somewhat intertwined with the protection/memory scheme that VAX/VMS
had].

What I meant by my comment is that, CMU took BSD 4.1, ripped out the memory
system and much of I/O system, and part of the process management system,
and then inserted Mach inside of it (aka Mach 2.5).    The UNIX API and
command system was left intact, and most of the basic UNIX kernel was left
alone.   They added a few new commands to and added some system services
for the "mach-ness" but as far as a user was concerned it was just BSD4.1
or later BSD 4.2.

What I was saying im my previous email was that I believe that trying to
pulling VAX/VMS apart in the same way as the CMU guys did to BSD, and
inserting a uKernel of almost any flavor into it under the covers would
have been much more difficult.​   Knowing a little about how both systems
were put together, I really believe that Unix was just much easier to
modify in that way and VMS was.


Clem
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.trailing-edge.com/pipermail/simh/attachments/20150304/227746d2/attachment.html>