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Date: Sat, 13 Mar 2004 21:11:28 -0800
From: David Schultz <das@FreeBSD.ORG>
To: "Daniel O'Connor" <doconnor@gsoft.com.au>
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	freebsd-chat@FreeBSD.ORG, Rob <rob@pythonemproject.com>
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cc: Rob <rob@pythonemproject.com>
cc: freebsd-chat@FreeBSD.ORG
Subject: Re: What makes Centrino so fast?
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On Thu, Mar 11, 2004, Daniel O'Connor wrote:
> On Thu, 11 Mar 2004 10:31, Rob wrote:
> > I have my own benchmark program that I use for number crunching.
> > It uses a mixture of Python and Numeric Python.
> >
> > Athlon 2166Mhz as reported by OS:  2m38.7s
> > Intel Centrino Pentium 1700 Mhz:   2m17s
> >
> > Is it just compiler optimization at play?
> 
> Here's an interesting article on it ->
> http://arstechnica.com/cpu/004/pentium-m/pentium-m-1.html
> 
> but in short.. better branch prediction, and micro-architecture improvments in 
> general, and a slightly longer pipeline (for higher clocks vs a PIII)

You're right that the longer pipeline allows the processor to be
clocked higher, but for a *given* speed (e.g. 1700 MHz), a longer
pipeline is actyually a disadvantage; longer pipelines cause more
stalls and higher branch misprediction costs.  The better branch
predition merely attempts to hide the penalty of the longer
pipeline.  I don't know why the Centrino performs better than the
Athlon in this case, though.  If you really care, you'll probably
have to factor the benchmark into specific, simple tests that
demonstrate the performance difference, play with compiler
optimizations, etc.