FYI
REAL-TIME COMPUTING--THE RTLINUX OPERATING SYSTEM                 
        
Linux is not a real-time operating system; it provides the best 
average response time: when it is loaded down, it gracefully degrades 
the performance of all running processes. In real-time computing, this 
is unacceptable. RTLinux is a Linux-based operating system that 
supports real-time computing. It is widely used as a desktop real-time 
OS, but it is less favorable as an embedded system. RTLinux is an open 
source product, distributed under the GPL terms. You can find more 
info about it and download its source code from: 

http://www.rtlinux.org/~rtlinux