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From: decot@hpisod2.HP.COM (Dave Decot)
Newsgroups: comp.unix.questions
Subject: Re: real-time Unix Systems
Message-ID: <10650006@hpisod2.HP.COM>
Date: Sat, 22-Aug-87 21:41:16 EDT
Article-I.D.: hpisod2.10650006
Posted: Sat Aug 22 21:41:16 1987
Date-Received: Sun, 23-Aug-87 23:49:18 EDT
References: <2663@bobkat.UUCP>
Organization: Hewlett Packard, Cupertino
Lines: 41

> 	I have looked at various real-time UNIX versions, and I do not
> care for them in OUR applications.  Why?  Because these real-time versions
> lack certain system calls and do NOT support many standard UNIX utilities.
> I feel that the usefulness of UNIX as a multi-user, multi-tasking system
> is that any user should be able to run what they want.  This is simply
> not true on any real-time UNIX system that I have seen.  For example,
> the last that I knew, there were NO real-time UNIX systems which would
> support `vi'.  How can you have UNIX without `vi'?  1/2 :-) 

All HP-UX systems support all SVID2 base system calls, many 4.2BSD
system calls, and `vi', since HP-UX is SVID Version 2 conforming.

In addition to the real-time features I described in an earlier response,
the new HP 9000/800 systems support sendmail, 4.2BSD job control and signals,
System V accounting, shell layers, X windows, SQL, IMAGE, the ARPA/Berkeley
networking facilities, and much more.  Various versions of Emacs are
available as contributed software.

> 	As a serious example, if I have a chemical process control system
> that is collecting data in real time, I feel that an engineer should be
> able to log into a terminal and run any spreadsheet or other program he
> wants with that data (at a lower priority, of course).  But I don't know
> of any real-time UNIX that is not essentially bound to specifically
> compiled application programs, some language support, and a simple editor.

The example you describe is easy on HP-UX (assuming chemctrl is properly
programmed, locks itself in memory, uses O_NDELAY on appropriate files, etc.):

    prealloc 10000000000 /tmp/chem     # reserve 10 Gigabytes fast file space
    rtprio 4 chemctrl > /tmp/chem &    # run chemctrl with realtime priority 4
    chemthink /tmp/foo > chem.123      # run data munger at timeshare priority
    lotus123 chem.123		       # run spreadsheet at timeshare priority

Disclaimer:
    Information purposes only.  Not a product offering/advertisement.
    I believe this stuff to be correct, but if there's money involved,
    ask a local HP representative.

Dave Decot
Hewlett-Packard
hpda!decot