Real-time UNIX - what is it & who has it?

[Adam Moskowitz]

I'm sure this has been asked before, but here goes again anyway . . .

A friend of mine has asked to help him locate a "real-time UN*X or UN*X-like
operating system".  I told him that VenturCom "claims" to sell such a beast,
but some discussion of their product ensued that led to the following
question:

    Assuming that you are doing something like data acquisition or
    process control, what is required to make an O/S "real-time"?

The answer he and I came up with was this: the ability to have absolute
control over the scheduling of processes.

Is there anything else we're missing?  I don't think so.  However, I'd love
to hear what other people think.  We're not saying that there aren't other
features that wouldn't be nice to have, but the heart of "real-time"-hood
comes down to scheduling.

So, given that, who makes what he needs?  We know that Charles River Data
Systems has something called UNOS that supposedly does that.  Does it?  Does
anyone else know of anything else that is available?

Since this might be a popular topic, I'll be sure to summarize whatever email
I get.  Thanx in advance.
-- 
Adam S. Moskowitz	            ...!(backbone)!{necntc,encore}!necis!adamm

     "Long long ago, in a galaxy far far away, God said, "Let there
      be lips!"  And there were lips.  And they were good!"  -- RHPS