Context Switch in Real Time Linux Vs VxWorks (or any other RTOS)

Gary Thomas gary at
Sat Jul 17 01:09:58 EST 2004

On Fri, 2004-07-16 at 00:50, Oliver Korpilla wrote:
> Arun Prasad Velu wrote:
> >
> >I am in the process of analyzing the feasibility of migrating an
> >existing VxWorks system (MPC860 target) to Linux (RTOS).
> >
> >I'd like to compare the features of Linux and VxWorks with respect to
> >the Real Time capabilities. I am little concerned about Linux's Context
> >Switching.
> >
> >I'd like to get your opinion on this. Even if I want to move to Linux,
> >I'll have to convince my management. So, any pointers on comparison of
> >Linux Vs VxWorks with respect to Real Time capabilities would be highly
> >appreciated.
> I hardly guess context switching will be your main problem, because the
> stock Linux kernel does not support hard realtime!
> You either have to use RTAI (free kernel modification that requires
> drivers to be rewritten for realtime), RTLinux (nearly the same,
> non-free, patented) or modified Linux kernels from TimeSys or MontaVista
> (who both add real-time capabilities in a more stock-Linux-compliant way).
> Depending on your target, eCos (a free embedded operating system with a
> focus on minimal code) may be the better choice for you, especially if
> your platform is already supported.

Thanks for the plug :-)  [n.b. I am one of the main eCos developers]
FYI, look to for details.

> Be warned: Not all PowerPC processors are supported in eCos (last time I
> checked 74xx and 7xx were missing).

Ah, but they are simple to add (and have been, but not necessarily
public) as they are effectively PPC60x processors with some differences.

Gary Thomas <gary at>
MLB Associates

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