|What does 32 bit application mean? firstname.lastname@example.org (Jatin Bhateja, Noida) (2005-07-28)|
|Re: What does 32 bit application mean? Juergen.Kahrs@vr-web.de (=?ISO-8859-1?Q?J=FCrgen_Kahrs?=) (2005-07-31)|
|Re: What does 32 bit application mean? DrDiettrich@compuserve.de (Hans-Peter Diettrich) (2005-07-31)|
|Re: What does 32 bit application mean? email@example.com (Florian Weimer) (2005-08-01)|
|Re: What does 32 bit application mean? firstname.lastname@example.org (Marco van de Voort) (2005-08-03)|
|Re: What does 32 bit application mean? email@example.com (Marco van de Voort) (2005-08-05)|
|Re: What does 32 bit application mean? firstname.lastname@example.org (Andi Kleen) (2005-08-05)|
|From:||Florian Weimer <email@example.com>|
|Date:||1 Aug 2005 15:20:33 -0400|
|Posted-Date:||01 Aug 2005 15:20:33 EDT|
* Jatin Bhateja:
> My question might sound trivial but I am not able to get an
> satisfying answer yet. Question is what do one understand when we
> say that an application is 32 bit or 64bit. Does this means that the
> compiler is compiled for 32 bit machine. If so this means that the
> application will use 32/64 bit registers. I have got two answers
> with me but I don't know exactly which one is correct. Kindly clear
> my doubt :
The term "32-bit application" mostly dates back to the days of
Windows 95, where it was used to differentiate between traditional
16-bit Windows applications and Win32 applications.
> Answer 1: When an application is compiled for and if the assembly
> generated by the compiler uses 32 bit register then we say that an
> application is 32 bit application. Thus it corresponds to the register
> size of an architecture.
> Answer 2: An application which contains 32 bit (virtual) addresses in
> its assembly is called an 32 bit application.
AFAIK, the terminology used to tell these two cases apart is
platform-dependent (both cases fall under the ILP32 model). On IRIX,
the first option is called the o32 ABI, and the second one is n32. I
believe Solaris/SPARC offers a similar choice.
Most operating systems supporting AMD64 do not currently offer such a
choice, which is a bit disappointing. The extended register set would
benefit ILP32 applications as well (which generally run faster because
smaller pointers result in a smaller working set).
> If my logical understanding is correct then can we make some tool
> such that if the compiler produces 64 bit code (contain 64 bit
> register) the tool will convert the 64 bit instructions to 32 bit
> instructions. Thus this 32 bit code can then be processed by
> assembler for 32 bit architecture.
This might work efficiently for some RISC architectures (but I doubt
it's worth the effort), but on AMD64, it will fail completely.
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