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Microcontroller Vs Microprocessor for RTOS

Started by Unknown January 31, 2005
Dear all,
I am just curious to know why almost all commercial popular RTOS like
RTLINUX,Vxworks work mainly on Micro processor instead of
Microcontrollers?
AFAIK,I have seen Vxworks work on Boards like Intel x86,powerpc,ARM and
all mentioned processor boards instead of real microcontrollers like
8051,68HC series from motorola and so.
Why do RTOS prefer microprocessors as compared to microcontrollers?

Though I know few RTOS like RTX-51 which runs exclusively only on 8051
microcontrollers,still such things are not so common in embedded world.

I would like to hear some real facts behind this decision instead of
starting a religious war of using microcontrollers or microprocessors
with RTOS...

Regards,
s.subbarayan

s_subbarayan@rediffmail.com wrote :

> Dear all, > I am just curious to know why almost all commercial popular RTOS > like RTLINUX,Vxworks work mainly on Micro processor instead of > Microcontrollers? > AFAIK,I have seen Vxworks work on Boards like Intel > x86,powerpc,ARM and all mentioned processor boards instead of real > microcontrollers like 8051,68HC series from motorola and so. > Why do RTOS prefer microprocessors as compared to > microcontrollers?
are you a sales person ? a manager (brr) ? those are basics - you DONT NEED an OS on something with 128 bytes of ram, you need every byte of resources. RTOS is a luxury Pozdrawiam. -- RusH // http://randki.o2.pl/profil.php?id_r=352019 Like ninjas, true hackers are shrouded in secrecy and mystery. You may never know -- UNTIL IT'S TOO LATE.
s_subbarayan@rediffmail.com wrote:
> Dear all, > I am just curious to know why almost all commercial popular RTOS like > RTLINUX,Vxworks work mainly on Micro processor instead of > Microcontrollers?
You mean "heavily advertised". Those two, in particular, are huge. The last time I checked VxWorks wasn't even available for anything less than a 32-bit processor. There are smaller micro kernels out there made for 8- and 16-bit processors (MicroC/OS is notable).
> AFAIK,I have seen Vxworks work on Boards like Intel x86,powerpc,ARM and > all mentioned processor boards instead of real microcontrollers like > 8051,68HC series from motorola and so. > Why do RTOS prefer microprocessors as compared to microcontrollers? >
Because the RTOS takes chip resources to run, and microprocessors generally have more resources to spend. Most significantly when you do a task swap you need to save the task's stack frame so you need storage for as many stack frames as you have separate tasks. This can suck up very large amounts of memory very quickly. Also, the benefits of an RTOS diminish as the application gets small, and microcontrollers are more likely to have small applications. For a small enough application you'll spend more time dinking with the RTOS to get it up and running than you'll save by having it there.
> Though I know few RTOS like RTX-51 which runs exclusively only on 8051 > microcontrollers,still such things are not so common in embedded world. > > I would like to hear some real facts behind this decision instead of > starting a religious war of using microcontrollers or microprocessors > with RTOS...
Hope springs eternal.
> > Regards, > s.subbarayan >
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
On 30 Jan 2005 21:36:22 -0800, s_subbarayan@rediffmail.com wrote:

>Dear all, >I am just curious to know why almost all commercial popular RTOS like >RTLINUX,Vxworks work mainly on Micro processor instead of >Microcontrollers?
I don't think they make such difference. Some companies even differ between microcontroller, embedded microprocessor and microprocessor. For an (RT)OS it is only interressting to know which architecture the CPU has, is it 8,16,32 or more bits, does it have an MMU or FPU etc. Esp. for VxWorks I know that it runs also on ARM base microcontrollers (taking the definition, that a microcontroller is an CPU + peripherals on the same chip). -- 42Bastian Do not email to bastian42@yahoo.com, it's a spam-only account :-) Use <same-name>@monlynx.de instead !
>AFAIK,I have seen Vxworks work on Boards like Intel x86,powerpc,ARM and >all mentioned processor boards instead of real microcontrollers like >8051,68HC series from motorola and so.
What is _your_ definition of a microcontroller ? Registersize ? Mine is: A microntroller is a cpu + periperals on the same chip.
>Though I know few RTOS like RTX-51 which runs exclusively only on 8051 >microcontrollers,still such things are not so common in embedded world.
Ouch, do you want to start another RTOS or not thread :-))
>I would like to hear some real facts behind this decision instead of >starting a religious war of using microcontrollers or microprocessors >with RTOS...
But it seems to. -- 42Bastian Do not email to bastian42@yahoo.com, it's a spam-only account :-) Use <same-name>@monlynx.de instead !
>>I would like to hear some real facts behind this decision i=ADnstead >>of starting a religious war of using microcontrollers or >>micro=ADprocessors with RTOS... >But it seems to.=20
Or rather a bragging session ?

s_subbarayan@rediffmail.com wrote:

> Dear all, > I am just curious to know why almost all commercial popular RTOS like > RTLINUX,Vxworks work mainly on Micro processor instead of > Microcontrollers? > AFAIK,I have seen Vxworks work on Boards like Intel x86,powerpc,ARM and > all mentioned processor boards instead of real microcontrollers like > 8051,68HC series from motorola and so. > Why do RTOS prefer microprocessors as compared to microcontrollers? > > Though I know few RTOS like RTX-51 which runs exclusively only on 8051 > microcontrollers,still such things are not so common in embedded world. > > I would like to hear some real facts behind this decision instead of > starting a religious war of using microcontrollers or microprocessors > with RTOS... > > Regards, > s.subbarayan
One Word "OVERHEAD"
Dear Subbu,

I think it may be this way if you are going for a specific applications
then the need for a specific controller comes into picture and then
they go for microcontrollers,

Usually an OS will be very generic and they operate on a generic
devices with so that the user will have a more flexibility for there
application but if you go for a microcontroller the devices on chip and
the controller will be very specific and the same code which is written
on the controller will have less portable options ,but if you consider
a pentium family for an example,if you have device driver for one
device on P3 the same code can be run on the P4 also.

Please let me know if i am wrong .
Thanks and Regard 
Prashanth B.S.