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  1. #1
    Registered User
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    ARMI and THUMB. What's the difference?

    What is the difference between ARMI and THUMB builds? Which one I must select to build the release of the application?

  2. #2
    Nokia Developer Champion
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    Smile Re: ARMI and THUMB. What's the difference?

    Hi,

    Both are used to generate instrcution set for ARM processor.
    While THUMB in nature results smaller code compare to ARMI and may be slower.

    Regards.
    Kiran.

  3. #3
    Registered User
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    Bengaluru, India
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    Re: ARMI and THUMB. What's the difference?

    ARMI vs ARM4 vs THUMB

    Current ARM processors (at least ARM7 and ARM9) have two instruction sets:
    one with instructions on 32 bits which is ARM4
    one 16 bits instructions which is THUMB

    ARM4 mode has a slightly richer instruction set. THUMB mode is more compact. A general rule is that program compiled in THUMB mode are smaller than program compiled in ARM4 mode. And program compiled in ARM4 are faster.

    However, this may not be true for all mobiles, depending on their hardware architecture. As a matter of fact, most mobile phones have a 16 bit memory bus, and then use THUMB mode. In that particular case, a THUMB mode program is generally smaller and quicker because one memory access is enough to fetch an instruction.

    ARMI stands for ARM Intermediate. This is the safest choice to use since ARMI program can be linked with THUMB or ARM4 libraries while THUMB compiled code can only be linked with THUMB code and ARM4 code with ARM4 code.

    Ref: NewLC - Overview of the Compilation system

  4. #4
    Registered User
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    Re: ARMI and THUMB. What's the difference?

    Quote Originally Posted by kiran10182
    Both are used to generate instrcution set for ARM processor.
    While THUMB in nature results smaller code compare to ARMI and may be slower.
    Quote Originally Posted by vin2ktalks
    ARMI vs ARM4 vs THUMB

    Current ARM processors (at least ARM7 and ARM9) have two instruction sets:
    one with instructions on 32 bits which is ARM4
    one 16 bits instructions which is THUMB

    ARM4 mode has a slightly richer instruction set. THUMB mode is more compact. A general rule is that program compiled in THUMB mode are smaller than program compiled in ARM4 mode. And program compiled in ARM4 are faster.

    However, this may not be true for all mobiles, depending on their hardware architecture. As a matter of fact, most mobile phones have a 16 bit memory bus, and then use THUMB mode. In that particular case, a THUMB mode program is generally smaller and quicker because one memory access is enough to fetch an instruction.

    ARMI stands for ARM Intermediate. This is the safest choice to use since ARMI program can be linked with THUMB or ARM4 libraries while THUMB compiled code can only be linked with THUMB code and ARM4 code with ARM4 code.

    Ref: NewLC - Overview of the Compilation system
    Thank You, vin2ktalks and kiran10182! Really useful info.
    But, I wonder how can I find out if my phone have 16bit or 32bit memory bus? My phone is Nokia'9500.

  5. #5
    Registered User
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    Sep 2006
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    8

    Re: ARMI and THUMB. What's the difference?

    There are device specific pages in the forum.nokia.com website and for a 9500 phone, it is http://forum.nokia.com/devices/9500 . Yours is a S80 2nd edition phone. Please check out the S80 SDK for more details. Hope it helps!

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