Intel Pentium M Centrino faster than Intel Pentium 4 ?

Intel Pentium M Centrino faster than Intel Pentium 4 ?

Post by Bad Discip » Thu, 14 Jul 2005 07:05:47


Hi folks,

Is it true that the processor Intel Pentium M Centrino system is faster
than the normal Intel Pentium 4 ? E.g. Intel Pentium M Centrino of
1.7GHz corresponds +/- to Intel Pentium 4 of 2.4GHZ ?

Thnx to feedback,
--
Bad Disciple
"O n e t h i n g I k n o w i s t h a t I k n o w n o t h i n g"
 
 
 

Intel Pentium M Centrino faster than Intel Pentium 4 ?

Post by usenetMYSH » Thu, 14 Jul 2005 07:27:54


: Hi folks,

: Is it true that the processor Intel Pentium M Centrino system is faster
: than the normal Intel Pentium 4 ? E.g. Intel Pentium M Centrino of
: 1.7GHz corresponds +/- to Intel Pentium 4 of 2.4GHZ ?

Yes, in effect, (1.7GHZ P-M closer to 3GHZ P4 I think) but there are a
couple of variables. For one, there are a couple of different
versions of Pentium M. The original, Banias, had only a 1MB cache;
the newer Dothan has a 2MB cache and will be a little faster perhaps
at the same clock speed.

Pentium M also does not have hyperthreading that the Pentium 4 has, so
when parallel tasks are executed, Pentium 4 has an advantage.

Andrew

 
 
 

Intel Pentium M Centrino faster than Intel Pentium 4 ?

Post by J. Clark » Thu, 14 Jul 2005 09:52:51


Not necessarily. Hypertheading is a crutch to get more performance out of
the very deep pipeline in the P4. The pipeline in the Pentium M is not as
deep, so hyperthreading would be less of an advantage.


--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
 
 
 

Intel Pentium M Centrino faster than Intel Pentium 4 ?

Post by Andrew » Thu, 14 Jul 2005 11:19:04


Yes.
 
 
 

Intel Pentium M Centrino faster than Intel Pentium 4 ?

Post by William Ko » Fri, 15 Jul 2005 04:05:40

"Bad Disciple" < XXXX@XXXXX.COM > wrote in



Surprisingly, yes. I can't find the article, but the reasons go something
like this. The Pentium M (Centrino) is based off the Pentium III core (or
one of them). This core is very successful with relatively low power
consumption, so after Intel decided to sideline the PIII, it continued to
be advanced as a low power chip and eventually evolved into Centrino. Why
did Intel sideline the PIII? Not sure, but probably because of something
to do with clock speeds. It wouldn't clock high enough at the time, or it
didn't extend to really high performance computing, or something like
that.

The Pentium IV was designed for high speed. Unfortunately, it has
problems. It is sort of like a race car that can go terribly fast on a
straight-away, but has trouble with the turns. In the PIV's case, to get
pure speed it has a very long pipeline (42 steps I think). The problem is
that if it mis-predicts a branch, the entire pipeline has to be discarded
and reloaded at a speed penalty. This apparently happens commonly enough
that, clock-for-clock, the Pentium M get's more done.

I wish I knew what stops them from pushing the PM's clock speed to those
of the PIV and have a faster processor with lower power consumption.

.wk.
 
 
 

Intel Pentium M Centrino faster than Intel Pentium 4 ?

Post by usenetMYSH » Fri, 15 Jul 2005 05:46:55


: Surprisingly, yes. I can't find the article, but the reasons go something
: like this. The Pentium M (Centrino) is based off the Pentium III core (or
: one of them). This core is very successful with relatively low power
: consumption, so after Intel decided to sideline the PIII, it continued to
: be advanced as a low power chip and eventually evolved into Centrino. Why
: did Intel sideline the PIII? Not sure, but probably because of something
: to do with clock speeds. It wouldn't clock high enough at the time, or it
: didn't extend to really high performance computing, or something like
: that.

Actually, the problem with the PIII was that it would not scale up in
frequency very well (hence your later question "Why can't they crank
up the Pentium M?"). During each pipeline stage, there's a certain
amount of work that the CPU does. As you increase the clock rate, you
reduce the amount of time in which that work can be done (OK, we're
talking picoseconds here - but still). The limiter in the clock rate
- one of them, anyway - is the minimum amount of time it takes to get
that work done in the slowest pipe stages. Maybe at 1.5GHZ there's
enough time to get the work done but not at 1.6GHZ - and if that work
can't be completed by the end of the pipe stage, the CPU will fail.

With the Pentium 4, Intel architects added more pipeline stages but
split up the work done in each stage more evenly, so the work could be
done more quickly and thus clock speed could be cranked up. So even
though it took more pipeline stages to get the same amount of work
done, you could also run the whole thing a lot faster. Unfortunately,
Intel's grand plans got snarled by power problems once the chip
operated above a certain frequency, so this scenerio kind of hit a
dead end. Thus the move to the Pentium M for laptop chips which are
the most sensitive to heat and power consumption and the move to
dual-core CPU desktop chips to improve performance. (FYI, you can
build yourself a Pentium M-based desktop now with motherboards from
DFI and AOpen. I am thinking about it.)

Pentium M actually has a lot of cool tricks built into it to reduce
power beyond the old PIII core. They slow down or stop parts of the
chip such as the front-side bus when it isn't needed. But in general,
a faster-clocked CPU eats more power, so the PIII core automatically
lent itself to lower power operation. But, the Pentium M is also
limited in how fast it can be clocked for the same reason as Pentium
III.

Lots of great information about this stuff is available at
http://www.yqcomputer.com/ .

Andrew