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Intel Pentium M Centrino faster than Intel Pentium 4 ?

Discussion in 'Laptops' started by Bad Disciple, Jul 12, 2005.

  1. Bad Disciple

    Bad Disciple Guest

    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, Jul 12, 2005
    #1
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  2. Bad Disciple

    Andrew Guest

    : 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
    --
    ----> Portland, Oregon, USA <----
    *******************************************************************
    ----> http://www.bizave.com <---- Photo Albums and Portland Info
    ----> To Email me remove "MYSHOES" from email address
    *******************************************************************
     
    Andrew, Jul 12, 2005
    #2
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  3. Bad Disciple

    J. Clarke Guest

    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.
     
    J. Clarke, Jul 13, 2005
    #3
  4. Bad Disciple

    Andrew J Guest

    Yes.
     
    Andrew J, Jul 13, 2005
    #4
  5. 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.
     
    William Korvine, Jul 13, 2005
    #5
  6. Bad Disciple

    Andrew Guest

    : 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.tomshardware.com .

    Andrew
    --
    ----> Portland, Oregon, USA <----
    *******************************************************************
    ----> http://www.bizave.com <---- Photo Albums and Portland Info
    ----> To Email me remove "MYSHOES" from email address
    *******************************************************************
     
    Andrew, Jul 13, 2005
    #6
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