2011 MBA's - i5 1.6 GHz vs i5 1.7 GHz

Discussion in 'MacBook Air' started by dmk1974, Sep 9, 2011.

  1. dmk1974 macrumors 68020


    Sep 16, 2008
    As I still contemplate which 2011 MBA I want to keep (the 11" with i5 1.6/4GB/128 GB or the 13" i5 1.7/4GB/128 GB), I'm wondering why I see such a huge difference in benchmark scores for the processors? I mean, it's only a 0.1 GHz differnece, but the Geekbench scores are like 20% higher for the 1.7 for some reason?

    And for further comparison, the MBP 2.3 i5 is then only 7% faster than the 1.7 (even though it's an additional 0.6 GHz faster processor). Am I just missing or not understanding something? Thanks!
  2. gloss macrumors 601


    May 9, 2006
    It's more than just clock speed. Bus speed, RAM cache, etc all play into overall processor performance.
  3. KPOM, Sep 9, 2011
    Last edited: Sep 9, 2011

    KPOM macrumors G5

    Oct 23, 2010
    The biggest difference is the Turbo Boost. The 1.6GHz processor boosts up to 2.0GHz with both cores running and 2.3GHz with one core running. The 1.7GHz processor boosts to 2.4GHz with both cores running and 2.7GHz with one core running. 2.4GHz is 20% faster than 2.0GHz, and that's the speed the processors are running at most of the time.

    All of those are the same between the two i5 models. The i7 model has 1MB extra cache, and boosts a little bit faster (2.6GHz in dual core and 2.9GHz in single core), but otherwise is the same, too.
  4. mountains macrumors regular

    Aug 26, 2011
    Intel lies about its processors' speeds. Really, it does.

    The 1.6 GHz i5 has a nominal speed of 1.6 GHz, but because of Intel's TurboBoost it's able to reach higher speeds as core temperature allows. It has a turbo multiplier of 0047, which means it can actually turbo up to 2.0 GHz (4 bins for 400 MHz turbo) with both cores active, or 2.3 GHz (7 bins for 700 MHz turbo) with one core active.

    The 1.7 GHz, however, happens to be a beast. It has a turbo multiplier of 007A, which means it can turbo up to 2.4 GHz (7 bins) with two cores active, or 2.7 GHz (10 bins; A represents 10 in hexidecimal) with one core active. So it may not look much faster than the 1.6 GHz i5, but the 1.7 is actually a whole lot faster.
  5. KPOM macrumors G5

    Oct 23, 2010
    It lies in a good way, however. They could probably legally argue that the 1.6GHz chip is a 2.0GHz chip, and the 1.7GHz chip is a 2.4GHz chip. For whatever reason, they don't.
  6. dmk1974 thread starter macrumors 68020


    Sep 16, 2008
    Thanks for the replies. So it's really the Turbo modes that differentiate the processors. Kinda screwy the way they rate them in listings, but I get it. Doesn't exactly make it easier in deciding between the 11" and 13" though. If the 11" was faster, it'd be a slam dunk for that one. I know I can get an i7 in 11", but don't really want to pay the extra.

    Here's a comparison I found on the Intel site:
  7. macbookpro45 macrumors 6502

    Jun 20, 2010
    Don't pay the extra. The marginal advantage you gain is offset by the cost you have to pay for the i7 anyway
  8. Razzz macrumors member

    Aug 6, 2011
    if you have the 11inch go for i7.
    for 13inch get the i5
  9. macbookpro45 macrumors 6502

    Jun 20, 2010
    What is the premise of your argument for suggesting this?
  10. vitzr macrumors 68030


    Jul 28, 2011
    Unless you're doing some very resource intensive work it's simply not worth it.

    Limited to only 4GB ram, you're not going to be able to take advantage of the full capabilities of that processor anyway.

    And if you do need the power, then you should be looking at a MacBook Pro.

    I use a new 15" MBP configured with 8GB & SSD, for my engineering and design work. For the rest, I use a new 13" MBA, that's a good combo.
  11. orfeas0 macrumors 6502a

    Aug 21, 2010
    Athens, Greece
    I wouldn't suggest an i7 in the 13inch. It's gonna get too hot.
  12. dmk1974 thread starter macrumors 68020


    Sep 16, 2008
    Yeah, I think I've ruled out an i7 in either size. Just gotta figure if I want a bit more power (13" w/i5 1.6) or portability (11" w/i5 1.6).
  13. KPOM macrumors G5

    Oct 23, 2010
    The CPU performance difference between the 1.6GHz i5 and 1.8GHz i7 is about 20-25%. The difference between the 1.7GHz i5 and 1.8GHz i7 is about 8-10%.
  14. ZBoater macrumors G3


    Jul 2, 2007
    Sunny Florida
    Ummmm, no, it will not. Or should I say it DOES not. :rolleyes:
  15. QuaziModo macrumors member

    Jul 25, 2011
    Townsville, Australia
    I completely agree with this. My 11" Ultimate does not get hot at all, unless I really am hammering it. The initial problems which people were reporting I think had to do with some thermal transfer issue which has since been sorted.

    I've got 6 desktops and apps on each of them right now and SMC says 48 degrees. It is barely warm on my lap right now.

    The decisions on middle run MBA's seems like a hard one to me as I need a machine for 3 years. Though if you are more lucky than I then perhaps a cheaper model every 18 months could work for you?
  16. richpjr macrumors 68030


    May 9, 2006
    Not my experience at all.

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