MMU

[Charles-Antoine Gauthier]

RTEMS is meant for hard real-time systems. Such systems do not do demand
paging because of the phenomenally high cost of fetching pages from disk
(relative to CPU speeds). Virtual memory may still be used. In some BSPs
with caches, the MMU is usually set up "to stay out of the way" as Joel
puts it, but it must be programmed to control the cache. Either some
form of block address translation is used, or page descriptors must be
set up.

One could also imagine setting up virtual addressing to build a flat
address space multiprocessor where each board uses the same fixed
physical addressing, as is common with many VME cards (IMHO usually due
to brain-damaged CPU designs).

Joel Sherrill wrote:
> 
> "Boris V. Guzhov" wrote:
> >
> > Hi All!
> >
> > Is there any sopport of the MMU in the RTEMS?
> 
> Only in the sense that some BSPs initialize MMUs
> to stay out of the way.
> 
> On a single CPU, RTEMS supports a POSIX model
> of a process with multiple threads.
> 
> This is a useful features that is critical for
> some embedded application classes.
> 
> > Boris V. Guzhov,
> > St.Petersburg
> 
> --
> Joel Sherrill, Ph.D.             Director of Research & Development
> joel at OARcorp.com                 On-Line Applications Research
> Ask me about RTEMS: a free RTOS  Huntsville AL 35805
>    Support Available             (256) 722-9985

-- 
Charles-Antoine Gauthier
Institute for Information Technology   Institut de technologie de
l'information
National Research Council of Canada    Conseil national de recherches du
Canada