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SubjectRe: RTAI/RtLinux
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In message <57.c083d0f.2a237c49@aol.com> Joachim Martillo wrote:
>
> Hardly seems surprising. Linux is a general purpose multiuser
> moderate weight multiprocessing preemptive time sliced time
> shared virtual memory operating system. Embedded system
> developers generally need single purpose extremely lightweight
> limited process count nonpreemptive cooperative real memory
> operating systems.

Joachim, your perception of "Embedded Systems" is not up to date.
There is a lot of devices which fall into this group that provide
resources you have been dreaming of for your workstation just 5 years
ago. For instance, your digital video recorder may have a 200+ MHz
PowerPC CPU, tens of megabytes RAM and tens of gigabytes harddisk
space. Can you remember the configuration of your fastest workstation
from 10 or 5 years ago?

Yes, there are embedded systems with limited resources where Linux is
just overkill. And probably (by number of units sold) these devices
are the majority.

But there are also lots of embedded devices that not only provide the
resources for a more powerful OS like Linux, but also demand it
because of the complexity of applications they are running. And if
you look at current trends you will find that this is one of the
fastest growing parts on the market.

> There is not so much overlap between the two types of
> operating systems. It is to the credit of the Linux design
> that with hacking Linux can generally be adapter to real
> time uses unlike some other common proprietary operating
> systems.

Again, this is not quite correct. There have been Real-Time and
Embedded Unix systems before (LynxOS, to name one). And there are
other "common proprietary operating systems" that can be adapted for
embedded needs (WinCE).

The big advantages of Linux are in defferent areas (free sources,
excellent support of all modern technologies, not single-sourced,
...).


The problems with Linux in Embedded and especially in Real-Time
Systems are not technical ones. It is the political situation, where
the user is left in uncertainty about what he can legally do and what
not.

And if you look at the (missing) answers to all specific questions
about this you can see that there is method to it. "Go and see a
lawyer" is all you get.

Hell, would you do busines with ANY company who tell you "ask your
laywer" when you ask for explanations of the conditions of use of
their products?

THIS is the main problem of Linux in the real-time market.


But who knows, maybe VY will provide clear "yes" / "no" answers this
time...

Wolfgang Denk

--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd@denx.de
Man did not weave the web of life; he is merely a strand in it.
Whatever he does to the web, he does to himself. - Seattle [1854]
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