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I wish to install Xenomai which works on Linux providing a kind of hard real time environment.

x86/64 architectures are supposed to contain the "System Management Mode" which prevents them from being used for hard real time systems.

By "System Management Mode" I mean this: http://en.wikipedia.org/wiki/System_Management_Mode

Do embedded boards like ARM also have this "System Management Mode"?
Answers with references will be appreciated.

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Note that time stolen by SMM on x86 systems running an acpi aware protected mode operating system generally is very close to nil, so generally does not interfere with real time operation, unless you have some ridiculously stringent real time requirements. –  psusi May 29 '12 at 22:51
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2 Answers 2

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System Management Mode is not the only thing that makes x86 bad at hard real time. The unpredictability of the execution speed due to caches, pipelines and so on makes x86, and any other high-end processor, bad at real time. All these features that make a processor fast on average also make the worst case difficult to manage.

The current generation of ARM chips is divided in three series: Cortex A for high-end microprocessors (the closest thing to x86), Cortex-R for real-time applications, and Cortex-M in a microcontroller profile. The Cortex-R does not have an MMU (some have an MPU) but may have a cache. It is used in many real-time applications (ARM tries to compete with DSPs, fairly successfully).

The ARM architecture itself does not define anything like SMM. It's possible that chip manufacturers add something like it, you'd have to look at the manufacturer's documentation.

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Thanks for the response. I was talking about TS-7800 ARM9 board. Should I provide any further information to help you to help me so that it becomes very clear that this board doesn't have the SMM? –  TheIndependentAquarius Jun 2 '12 at 7:46
    
@AnishaKaul Oh, it's absolutely clear that the TS-7800 doesn't have SMM: SMM is an x86 feature, and the TS-7800 doesn't have an x86 processor. If your question is whether it's suitable for your real-time application, that depends on what your application is (a medical device, a telephony system, a TV, …). I suggest you ask a more precise question on Electrical Engineering, where the experts are. –  Gilles Jun 2 '12 at 13:31
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See the section on Exceptions and Interrupts here: http://wiki.osdev.org/ARM_Overview#Exceptions.2C_IRQs_and_Software_Interrupts_on_ARMv4_and_up

Basically, the answer is no. ARM CPUs do not have a "System Management Mode" or SMM. On ARM CPUs, the OS kernel handles the interrupts.

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That's not exactly true: on ARM CPUs with TrustZone, FIQs are caught by the secure world, so the monitor can process them, which is analogous to SMM. –  Gilles May 30 '12 at 1:49
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