32bit vs 64bit

Kam Leo kam.leo at gmail.com
Wed Sep 17 21:49:02 UTC 2008


On Wed, Sep 17, 2008 at 1:51 PM, Bill Davidsen <davidsen at tmr.com> wrote:
> Bingo wrote:
>>
>> Read this for a comparison in performance for 32 bit, and 64 bit linux:
>> http://bingouv.blogspot.com/2008/08/desktop-linux-performance-comparison32.html
>> .
>>
>> To summarize, you will notice the difference between 32 bit and 64 bit for
>> CPU intensive tasks. But it won't change the world. This comparison is based
>> on Fedora-9.
>>
> One thing that most people undervalue is that almost none of these tests are
> actually done on 32 bit and 64 bit processors, they are widely done on the
> same processor (to keep thing the same) and the 32 bit test is run on a 64
> bit CPU in 32 bit mode.
>
> This is important because the big difference between 8 and 16 bit, or 16 and
> 32 bit was the longer registers and wider path to memory. And so the tests
> were run on different CPUs. Running the test on the same CPU in two modes
> gives far less improvement, and most recent tests measure only the
> difference between modes.
>
> Since the three advantages of 64 bit operation are lower overhead with large
> memory, ability to run larger user images, and a few more 64 bit registers,
> it's not surprising that the benefits are not huge, and that many systems
> will just not see any measurable difference, due to a lack of large
> processes or memory. The overhead of PAE operation is generally hard to find
> in the noise.
>
> Obviously there are loads which do show a larger difference, and some of
> those loads are "real loads" rather than benchmarks and test cases, but for
> most configurations and loads it can be "measured but not felt."
>
> Note: this is just to remind people of the factors involved, not to agree or
> disagree with anyone.
>
> --
> Bill Davidsen <davidsen at tmr.com>
>

I believe the discussion is i386 (32-bit) vs. x64 (64-bit extended
instruction mode for x86 processors). Dual booting the i386 and x64
versions of the OS on the same hardware should make a level playing
field.




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