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The difference between RTOS and general purpose OS?

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Rajesh

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Operating system

Main difference between RTOS and general purpose OS?


Note!
Nothing to do with ' EDA E-books Upload/Download ' section. Moved here.

--
mw
 

Re: Operating system

Hi

For RTOS, time scheduling is guaranteed between two consecutive ticks, for example 10ms or 25ms, whereas for OS like windows NT or 2K, the mean time tick is guarenteed on a long time period but not beetween two consecutive ticks.

Papyaki
 

Re: Operating system

refer the nelow links for more information.

**broken link removed**
**broken link removed**
 

Re: Operating system

For example, if you need to use RTOS to control Robot ARM/ABS... something need to be served within the specify time, use RTOS.
If all the served tasks are not time critical, use general OS is enough.
 

Re: Operating system

RTOS provide real-time multi-task and communication scheme between the tasks,
 

Re: Operating system

hichen said:
RTOS provide real-time multi-task and communication scheme between the tasks,
Click to expand...

You explain RTOS just by it's name "real time OS".
You didn't explain what is "real time" mean?
 

Re: Operating system

jamesyang1209 said:
hichen said:
RTOS provide real-time multi-task and communication scheme between the tasks,
Click to expand...

You explain RTOS just by it's name "real time OS".
You didn't explain what is "real time" mean?
Click to expand...

Ok, let suppouse you are making a robot with two hands - one is throwing a glass beer bottle up and second arm is catching this bottle in the fly.

If you will control hands in MS Windows, then all bottles will be broken no beer will be left. But if you install QNX then all of them will be safe. That is why Microsoft is a big danger for the World! :)

Now you see what is "real time" - it is time in real world.
 

Re: Operating system

klug said:
jamesyang1209 said:
hichen said:
RTOS provide real-time multi-task and communication scheme between the tasks,
Click to expand...

You explain RTOS just by it's name "real time OS".
You didn't explain what is "real time" mean?
Click to expand...

Ok, let suppouse you are making a robot with two hands - one is throwing a glass beer bottle up and second arm is catching this bottle in the fly.

If you will control hands in MS Windows, then all bottles will be broken no beer will be left. But if you install QNX then all of them will be safe. That is why Microsoft is a big danger for the World! :)

Now you see what is "real time" - it is time in real world.
Click to expand...

No.
The "real time" don't mean "it's time in real world".
In RTOS, the first priority task must be served within a guarantee time.
That is, "real time" is more close to "on time" and "within a time".
 

Re: Operating system

Broadly-speaking, RTOSs are designed to respond as quickly as possible to interrupts, and to provide prioritised tasks, so that if your design needs 1-to-10us-ish response times, and/or has activities which must be completed as quickly as possible, then it is possible. Of course, if your design has a high-priority interrupt or task that takes a certain amount of time (e.g. 10ms), it will still lock out lower-priority interrupts or tasks for that time; an RTOS can't *guarantee* a certain response time, so you still have to design carefully.

Similarly generalising, Windows, Solaris, and other general-purpose OSs aren't designed to respond this quickly; they are designed to work more in human-time, 100-to-1000ms-ish.

HTH
Barny
 

Re: Operating system

jamesyang1209 said:
The "real time" don't mean "it's time in real world".
In RTOS, the first priority task must be served within a guarantee time.
That is, "real time" is more close to "on time" and "within a time".
Click to expand...

That s te right explanation. :spoko:
"Real Time" has nothing to do with "speed"
 

Re: Operating system

Hi,

RTOSs are used more like to guarantee real time response, especially for hard real-time systems, where a 1ms delay of the response is just as severe as a two week delay or no response at all. And as a remark, interrupt response time isn't an issue regarding RTOSs, as they are to be avoided as much as possible, due to the uncontrollable execution times of ISRs that can lead to missing some of the tasks deadlines.

Regards
 

Re: Operating system

Another difference between RTOS and general-purpose OS is that the latter often provide virtual memory which means that a much greater amount of apparent memory than the actual physical memory is provided to applications; the data stored in the virtual memory is actually stored on disk and brought into physical memory only when it is actually needed, a process called 'paging'.

This allows many more applications to be run (because more 'memory' is available) but the downside is that because data may have to be read from disk before it is accessible, there may be pauses in execution of e.g. 10-20ms or more. These OSs usually provide ways for applications to ensure that their code and data is always in memory, so that quickish response is possible, but it all gets a lot more complicated...
 

Operating system

Real time oS responds quıckly
OS can respond with a delay
 

Re: Operating system

There is no real time OS. There is only real time systems. Never split system to OS and application. For hard real time system, certain task must be done in time. RTOS mean a operating systems that is more possible to realize a real time system.
 

Operating system

"real time" is a depend on the application that use for. not on operating system.

for example if you have a device that generate signal every 1ms and you have to process this signal immeditaly before the next signal arrive , and you could do it with normal pc!! , therefore the pc become real time system and the platform become real time operating system.

for example voice compression unit time is 20ms , therefore the system should finish processing every 20ms before the next samples be ready. if the system can achive this it become real time if not then it is not real time system.

conculosion :

any system become "real time" if it can handle your unit time process (1s , 1ms, 10ms, 1us.......etc)
 

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