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Re: Realtime OS needed



On Tue, Apr 08, 2003 at 11:57:09AM +0200, martin f krafft wrote:
> Folks,
> 
> We are building a robot, and have been advised to use QNX
> (www.qnx.com) for that. QNX is a real-time OS that claims POSIX
> compliance. All nice and well, but I want APT and my familiar Linux
> environment.
> 
> I know that there are realtime patches for Linux floating around. So
> I am wondering if any of you have had experience with any of those
> patches. Are they reliable and usable, and do they allow my
> controllers to run in real-time while I can still maintain the box
> with my Debian knowledge?
> 
> Lastly: does anyone have a good document covering realtime, what
> it's needs are, and what it does? I know that realtime means that
> processes don't get put in a queue but run immediately. How that
> works with a multi-tasking OS is a bit foggy to me. Moreover, what's
> the difference between a process on a realtime OS, and one with
> nice -20?

I don't know much about it, but AFAIK the realtime patches basically
implement a new scheduler that sits under the kernel, and the realtime
processes run beside the kernel. 
There is some info at
http://www.realtime-info.be/encyc/rtlinux/RealtimeLinux.htm
with links to both competing implementations (rtlinux and rtai)
http://www.rtlinux.org seems to be unreachable, but http://www.rtlinux.com
is live.

Note that I have never used either of them. My knowledge comes mostly
from flamewars on LKML.

Frank

> 
> Thanks!
> 
> -- 
> Please do not CC me when replying to lists; I read them!
>  
>  .''`.     martin f. krafft <madduck@debian.org>
> : :'  :    proud Debian developer, admin, and user
> `. `'`
>   `-  Debian - when you have better things to do than fixing a system
>  
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