IBM and Univac Unix

[zben at umcp-cs.UUCP]

[There is a large, oversized SHell between you and your Unix...]

Credentials: Systems Programmer on Univac 1100s since 1972.
             Paper published in CACM June 1975.
             Implementor of Software Tools version for Univac 1100
              currently distributed by software tools user's group.

Scuttlebutt (private communication with Univac insider) claims Univac
bought Unix back from Bell and is developing it internally.  Article
for which this is a followup claims Bell is developing it internally. 
All that follows is based upon the version we have (but do not run)
here at UOM.

Its pretty amazing folks.  They actually do all of Unix, including raw IO
to terminals (if you run a Unix CCR) and the stopping and single-stepping
of processes.  Sort of.  Only one process on the whole machine seems to be
able to do it, but this is more an indictment of the Univac interprocess
communication mechanism (or lack of same) than anything else.

Still, you're going to be able to run just about half as many users under
Unix as you could under the bare operating system.  This might not be that
unreasonable.  I have it on good authority (from performance analysis freaks)
that on a 4341 you waste about half your cycles by using VM rather than one
of the more efficient IBM operating systems, and (from another source)
that you can run about double the number of users on your vaxen were you
to run VMS rather than Unix.

There are also enormous gaping security holes in Univac Unix.  This might
not bother you terribly much as Unix seems to be wide open anyway, but
consider the fact that I can write a 3 line C program that destroys an
entire filesystem and there is nothing the system can do to prevent it.
(For those who would understand, try CSF$('@FREE,D <FILESYSTEMNAME>.').

There are some things that could be done to improve both the performance
and security of this product.  Undoutably Bell is working on it.  Again
rumor is that 50 users totally saturate an 1100/84, while we were running
177 on our 1100/82 (half as many CPUs) yesterday afternoon.  I'm sure Bell
doesn't like this any more than I do.  Perhaps more importantly, Univac
seems to be "migrating" its operating system to be able to do the things
that Unix needs to do to improve both its performance and security.  About
two or three years down the pike Unix might be a very respectable product.

I guess you pays your money and takes your chances.  You have a tradeoff
between absolute number of users you can handle, and what those users can
do once they get on.  Security may or may not be important in your
particular environment.  Each site must make its own choice...
-- 
Ben Cranston   ...seismo!umcp-cs!zben      zben at umd2.ARPA