> On 22/06/2011 06:40 PM, Warp wrote:
>
>> The official benchmark results are also interesting. It's incredible how
>> much faster a Xeon W3580 is than a Pentium 4 (which is what I have) at
>> the
>> same clockrate, even when using just one core. While the latter takes
>> about
>> 25 minutes to render the benchmark, the former takes only a bit over 1
>> minute.
>>
>> That's some *serious* speedup considering that they are running at the
>> same clock rate.
>
> It puzzles me how this is possible.
>
> Sure, the Xeon probably has a much bigger cache and a slightly faster
> bus to the RAM chips. But is that *all* that makes it faster? Or is
> there more to it than that? I have no idea.
>

The Pentium 4 line is notorious ineffecient in it's use of the clock 
cycles, and each of it's generations just got worst of than the previous 
one. The problem was coined to an excessively long instruction pipe, 
that got longer with each sub versions. It topped at over 200 steps... 
It also greatly increased it's power requirments.

With the new core2, they chopped that down around 30~40 steps with the 
performance boost, and power consumption decrease, we can now experiment.

A Xeon system use a more advanced I/O architecture and beter memory 
management. It's instruction pipe is relatively short. It probably have 
beter cache management as well as larger cache, both L1 and L2. It's L1 
cache is probably distinct to the L2 cache, while the pentiums L1 cache 
address space was included in the L2 address space.


Alain

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