> Alain <ele### [at] netscapenet> wrote:
>> It's not realy about speed, but about RAM access capacity.
>> With the 32 bits version, there is an absolute limit of 4Gb for the amount of
>> RAM available, more like 2 to 3 Gb due to various OS limitations.
>> With the 64 bits version, that limit disapears, BUT, you also must be running a
>> 64 bits OS on a 64 bits CPU, with enough RAM installed.
>>
>> This can come to a faster rendering IF you have a scene that need LOTS of space
>> in memory (over 4Gb), have all the memory installed and can prevent the use of
>> the swap file. Such a scene just CAN'T be rendered on a 32 bits system.
>>
>> Any gain in speed don't come from the 64 bits processing, but from the generaly
>> more clock effecient 64 bits processors.
>>
>> --
>> Alain
>> -------------------------------------------------
>> You know you've been raytracing too long when your idea of a complete computer
>> is a fast CPU, lots of RAM, and a means of running POVray.
>> Aaron Gage a.k.a Slartibartfast
> 
> I know it's been a long long time, but I just wanted to add to this conversation
> that fact that the 64 bit processors also have several more registers than the
> IA-32 counterparts.
> 
> So with 64 bit you get more memory access, and more registers on the "good"
> side.  On the "bad" side is the fact that all pointers are now 8 bytes, which
> may negatively affect your data cache performance.
> 
> --Keith Brafford
> 
> 
True, but 64 bits CPUs also have more cache than the 32s.
So, while you put about twice as much data in the cache, that cache is 
often 2 to 4 times larger... and have a 64 bits data pipe.


Alain

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