free RTOS for embedded PowerPC with TCP stack needed

Joel Sherrill
Thu Feb 5 06:06:00 GMT 1998

On Thu, 29 Jan 1998, THIEBOLT Francois wrote:

> Well, now this chain works (Linux), i'd like to find a free RTOS which
> include a TCP stack (even i'll try to build my own), so any idea ???
> I've always heard about RTEMS, but is there any others and what makes
> them different ?

I would guess the top 3 candidates for a free RTOS are (alphabetical
order) RTEMS, uCOS, and VSTa.  Here is what I know about them and remember
I am one of the RTEMS developers, so I obviously know more about it. :)

uCOS is Jean Labrosse' small RTOS.  It has minimal features, is small, and
each port has its own source tree.  He has written a book on it and has at
least one other book on embedded software.  I do not know of any official
support available for it.  I noticed in the Embedded Systems show advance
program that he now works for Microtec.

I don't know much about VSTa.  I think it is only for ix86's and I do not
know if there are any claims that it is real-time. The source is at  I apologize for not remembering the
author's name.

RTEMS is based on the same standard that pSOS+ was.  It also includes
support for POSIX threads and multiprocessing.  It is configurable and
parts can be left out.  It has been ported to the m68k, i386, i960, sparc,
powerpc, mips, hp pa-risc, and amd 29k.  The cpu specific code is small
and well-contained with all ports sharing the same source tree.  There are
about 20 Board Support Packages in the tree now. The interrupt latency is
low and performance is deterministic.  We use newlib as a C library and
use its reentrancy support.  There is a test suite which is intended to
provide 100% source code coverage.  The current source includes a TCP/IP
stack, C++ class wrappers for the "classic" API, configuration via GNU
autoconf,  and a host of other improvements.  When it is ready, it will
be publicly released.  As of right now, each snapshot has had a decreasing
number of minor build problems the development team has wanted to fix
before the code was made widely available.  

The biggest distinctions of RTEMS are that it is actively supported,
supports GNAT and has passed international validation, and has
increasingly good support in the GNU tool chain.  

Joel Sherrill                    Director of Research & Development                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
   Support Available             (205) 722-9985

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