Concurrent Controls Multiuser DOS

[Jonathan Haddox]

I'm researching Multiuser DOS out of my own interest.  A version made by Concurrent Controls specifically.  However, I have been unable to find documentation on it to satisfy my curiosity on how it works and how it is configured.  They must have somehow broken the 640K barrier or virtualized each user session, I'd like to understand it better.  What were it's limitations, I'm guessing that each user didn't get direct access to hardware.  Anyone out there have a document or experience with it?  

Thanks,

Jonathan