Help: Some rtems basic questions... sorry...

Steven Johnson sjohnson at
Wed Jan 14 22:19:14 UTC 2004

Alex wrote:
 > Hi all,
 > I am a beginner in the rtems kernell... I have reading some documents but I cant
 > solution some doubts:
 > My doubts are:Does RTEMS has user space and kernell space?
NO.  Rtems is more an Executive than an OS like Linux.  The OS and Application 
have the same level of access to the hardware. (Which is a good thing for 
embedded systems).

 > Does RTEMS suppoorts more than one process running at a time?
RTEMS does not have processes per se.  It has tasks, tasks are really the same 
as threads in RTEMS Speak.  So you can have a "FTP" Task, which has its own 
exeuction context and a "Main Application" task that has another.  Processes are 
not required.  Again, this is a good thing for embedded systems as it is a lot 

 > Does RTEMS has memory protection? virtual address partitions?
No, not natively.  But there is nothing stopping you using an MMU in your 
application if you require.

 > Does rtems supports interrupt nesting...?
Depends on the Processor/BSP.  But the short answer is YES.

 > Sorry about this simple questions, but I cant have sure about this?
 > Any special document to read? Any advices?
RTEMS is not like the Linux Kernel, RTEMS is a library you link to your 
application, that gives you OS features.  It is very light and fast, and ideal 
for embedded applications.  It is not a desktop operating system.

 > Am trying the BSP for i686
Others might be able to tell you about RTEMS on x86, i've never used it there.

 > Many thanks
 > Alex


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