Path: utzoo!attcan!uunet!cs.utexas.edu!sun-barr!ames!mailrus!iuvax!watmath!focsys!larry
From: larry@focsys.UUCP (Larry Williamson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: QNX Operating System
Summary: It really is very good.
Keywords: operating system
Message-ID: <445@focsys.UUCP>
Date: 12 May 89 17:40:16 GMT
References: <634@pmafire.UUCP>
Reply-To: larry@focsys.UUCP (Larry Williamson)
Organization: Focus Automation Systems, Waterloo, Ontario.
Lines: 81

In article <634@pmafire.UUCP> alan@pmafire.UUCP (alan herbst) writes:
>
>Does anyone have any experience with the QNX operating system by Quantum 

I used qnx for about 2 1/2 years at my previous employ. It was quite a
good system. Fast, small, easy to use. Not quite unix, but there are
quite a lot of similarities.

It will not support 32 interactive users that are really doing anything,
no more than unix or xenix on an AT can. But with the right smart card,
(the intellicon-8 from Connect Tech Inc.) you can go a long way. I mention
the Intellicon-8 only because its qnx drivers are amazingly good. They
support most of the interactive command line editing right in the card.
Qnx does not get any interrupts until 'enter' is pressed.

Qnx does support an amazing number of tasks. It runs in protected mode on
an AT. You don't get perfect task protection, but then the AT does not
allow that anyway. The scheduling algorithm is different from unix in
that a task of given priority will always run if ready if there are no
tasks of a higher or equal priority. If two or more tasks have equal
priority, they will all get equal share of the cpu (assuming they don't
block on i/o or something). The scheduling is somewhat deterministic.
This makes it good for real time applications.

But what really makes qnx shine is the networking.  Qnx was designed
with the network in mind as an intregral part of the system.  You can
share more than just disks, but any hardware resource, including the
cpu itself! And quite transparently too.  The lan is token ring based
arcnet.  Extremely fast.  The system that I worked with was a network
of about 50 AT's and a couple of XT's.  Most of the machines had no
disk drives.  They would boot from the network, get all their commands
from the network, the user's home directories were scattered all over
the (approx) dozen drives on the network.  Tape backups were done from
just two of the machines. 

You can execute commands on remote nodes, have stderr report to
another remote node, have stdin read from yet another remote node and
have stdout come to your own terminal. 

Tasks communicate with each other through a message passing mechanism. 
It is rather primitive, but extremely reliable.  The first thing we
did was write a non-blocking mailbox scheme that ran on top of the
built in message system.  (Patterned after Intel's RMX-86 mailboxes). 
This improved the functionality of the intertask communications quite
a bit. 

The location of a task that you wish to communicate with can be kept
transparent, ie the caller does not need to know that the receiver is
on this or any other node.

We found that with proper distribution of tasks across the network, we
could quite easily improve the performance of the system. Although
we were adding a network overhead on messages, with careful planning
there would be less load on each cpu so that it could execute the
appropriate tasks with less interference. And because the network is
so transparent, you can move tasks around from node to node without
any recompiles or relinks or edits, etc.

Last but most important, Quantum's technical support is "second to none"!

It was my misfortune to experience the extreme excellence of their
support before I was exposed to the appalling state of affairs in the
unix world.  By comparison, you get NO support of any kind from any of
the unix vendors I've met.  Whereas, with Quantum, if you have a
problem, they will bend over backwards to help you through it. There
were times we would report a bug in the os and Quantum would have
a new version, fixed for us to download the same day!! Though next
day service was more common.

If you have any specific questions, please feel free to contact me. 
Be aware though that I don't have much experience with the most
recent release of qnx.  There have been quite a few rather big
improvements (along the line of the differences from V7 to R2 or
from R2 to R3 of unix system V). 

All in all, I found qnx to be an excellent product to work with.

-Larry
-- 
Larry Williamson  -- Focus Systems -- Waterloo, Ontario
                  watmath!focsys!larry  (519) 746-4918