13" MBP Retina - i5 v. i7 battery life

Discussion in 'MacBook Pro' started by mok749, Oct 22, 2013.

  1. mok749 macrumors newbie

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    Dec 3, 2010
    #1
    Trying to decide between the i5 2.6Ghz and the i7 2.8GHz.

    According the Anandtech, for the MBA, the battery life for the i5 is 18% better than the i7 on heavy loads.

    http://www.anandtech.com/show/7113/2013-macbook-air-core-i5-4250u-vs-core-i7-4650u/4

    Do you think that it's the same for the 13" MBP too?

    Anyone know much the i7 boosts performance? I searched the net for benchmarks on those CPUs (i7-4558U v. i5-4288U), but came up with nothing.
     
  2. Atomic Walrus macrumors 6502a

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    Sep 24, 2012
    #2
    Remember that while the battery life was ~18% worse on the i7, it also was about ~20% faster (variable depending on the task, but the article calls it 20% overall). Meaning in practice if you have a set amount of processing work to be done that takes 100 seconds on the i5 chip, it will take ~80 seconds on the i7. In the end about the same amount of power will have been used, but one will have finished slightly sooner.

    That's a simplified theoretical example of course. In reality I have to expect that the i7 does have some efficiency losses when you actually look at 100% load situations (Anandtech's "heavy" usage test is not a constant 100% CPU load). To really understand the relative efficiency of the two chips under load you'd have to determine the ratio: (processing work units) / (consumed power unit). This would require running battery life tests at 100% load on both chips, which is something I'd like to see Anandtech do in the future.
     
  3. waitingallday macrumors member

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    Jun 6, 2007
    #3
    Wow…I'm kinda surprised by that much of a difference in speed vs. battery.
     
  4. mok749 thread starter macrumors newbie

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    Dec 3, 2010
    #4
    I thought so at first too. But Anandtech made sure that the total work done was the same for both the i5 and i7:

    "What's important to note about all of these tests is that the amount of work done per cycle of the test doesn't vary based on performance. There's enough idle time baked in to make sure that the Core i7 based 13-inch MBA isn't artifically penalized by having to do more work than the i5 model simply because it's faster."

    So even though the i7 finished the work faster, and could go into idle mode faster, it still used 18% more energy for the same amount of work.
     
  5. Hexoic macrumors newbie

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    Aug 29, 2013
    #5

    I'm pondering the same choice as the OP. I tend to work my laptop pretty hard, but the question is at what point does it make a difference? I run lots of adobe apps at the same time and generally have lots of stuff open. The points where using my old 2010 MBP 13" gets painful is- rendering visual effects in PS and AI and saving/opening/etc big files. I guess the latter is solved by switching to SSD. But when you've got 50 objects in AI all with separate raster effects, and you have to wait for each and every one of them to render whenever you change anything.. it gets tedious. Would going for the i7 2.8Ghz choice improve this?

    also, how do the Iris graphics compare to my ol' NVIDIA GeForce 320M ? just because that's my reference point...
     
  6. teotuf macrumors member

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    Jan 24, 2012
    #6
    better. it would be more in line with the 330m found in the 15 inch from that gen
     
  7. Hexoic macrumors newbie

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    Aug 29, 2013
    #7
    so iris is as good as 15" MBP graphics from three years ago..??
     
  8. teotuf macrumors member

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    Jan 24, 2012
    #8
    Iris pro in the 15 inch is a little weaker 650m from last year, but it should be much better than the 6750m found in the 2011 mbp, and leaps ahead of the 330m.
     
  9. Leudast macrumors member

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    Feb 17, 2011
    #9
    I'm also wavering between the two. I wish there were some benchmarks in this specific machine to help the decision.

    I'm going to try to get into some light to medium photoshop, and some very light gaming, with a lot of multitasking standard consumer crap.

    Which would be better for my needs? 2.6/2.8?
     
  10. teotuf macrumors member

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    Jan 24, 2012
    #10
    Unless you specifically need the 4mb L3 cache, go with the 2.6ghz. It's barely 3-5% faster in cinebench and geekbench when stressed to the max. For everyday use you won't notice any difference at all.
     
  11. mitch1211 macrumors newbie

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    Feb 9, 2013
    #11
    I found this link helpful http://www.cpu-world.com/Compare/87...5-4288U_vs_Intel_Core_i7_Mobile_i7-4558U.html

    Seems the main advantages are a larger cache memory and slightly higher physical clock speed. The power consumed by each appears to be equal.

    I'm also tossing up between the i5 or the i7, I use a lot of spreadsheets will a tonne of numbers, also matlab and a little bit of programming.

    Do you think its worth the upgrade for me?
     
  12. cypherpunks01 macrumors newbie

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    Jun 27, 2012
    #12
    You need to keep in mind that both i5 and i7 CPUs of macbook air had the same 15W TDP. Which means same as in your link: in “theory” they consume equal energy.

    In practice as real-world tests shown, this is simply not true. i7 consumes 18% more battery and I think this will be true for MBPr too. I won't recommend it if you want decent battery life.
     
  13. T-Bob macrumors 6502

    T-Bob

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    Oct 23, 2013
    #13
    Yes it is hard to decide with so little detailed information out there.

    Just went for the 2.6/16/512 option myself. The extra GPU clock makes it a must have over 2.4 but not seeing the same draw for the i7 with that price difference.


    Completely agree. TDP is just the envelope that the range is expected to perform within. Actual use usually differs.
     
  14. mrmors macrumors member

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    Jul 29, 2011
    #14
    Geekbench seems to saying that the i5 can get 3189 and the i7 3798, so about a 19% boost from a 2.6 i5 to a 2.8 i7
     
  15. Atomic Walrus macrumors 6502a

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    Sep 24, 2012
    #15
    Yeah, I'm not sure where people are getting the idea that TDP is some kind of average or target power consumption. It's the limit, and even then it's a soft limit when the thermal situation is good.

    Consider a single core at 100% load: They're all going to consume less than 28W so the TDP is meaningless, and they're all going to consume different amounts of power because they're at different clocks. Even with both cores loaded most of the time the TDP doesn't matter (because the chips will go over 28W unless they're too hot).
     
  16. AlecMyrddyn macrumors 6502

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    Southern Maine
    #16
    Can you link to those scores? I can't find them. Keep in mind you need to look at the average scores for a specific model, not the highest individual score.

    http://browser.primatelabs.com/mac-benchmarks (as of today, November 1, 2013) is showing average results on their Geekbench 3 chart as follows:"

    Proc | 32 Single | 32 Multi | 64 Single | 64 Multi
    2.8 GHz i7 | 2997 | 6066 | 3285 | 6901
    2.6 GHz i5 | 2832 | 5850 | 3105 | 6610
    2.4 GHz i5 | 2661 | 5472 | 2932 | 6184
     
  17. Mots macrumors newbie

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    Oct 29, 2013
    #17
    So does this make it worth the upgrade to an i7 in your opinion? I'm pretty new to this stuff and have modest usage needs, like light video editing and possibly light gaming. I would really like to get the most out of that little 13-incher on those tasks though as the 15-inch model is not an option for me.
     
  18. T-Bob macrumors 6502

    T-Bob

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    Oct 23, 2013
    #18
    Based on those scores it is less of a jump from 2.4, but that is only Geekbench. We really need through metrics from a site like Anandtech to get the full picture, or comparison benchmarks.

    Went to apple store yesterday for IRL look and was told that benchmarks mean nothing and will make no difference to experience. Glad I benefited from genius wisdom :rolleyes:
     
  19. PDFierro macrumors 68040

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    Sep 8, 2009
    #19
    Yeah, I was playing with the 2.4 at the store and it was plenty fast.
     
  20. AlecMyrddyn macrumors 6502

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    Southern Maine
    #20
    You get a CPU performance increase of roughly 6 to 7% by upgrading from the 2.4 to 2.6 i5. You also get a bump in the maximum Iris GPU frequency of 1100 to 1200 MHz.

    The bump from the 2.6 i5 to 2.8 i7 is between 4 and 6%, and the i7 has 25% more L3 cache (4 MB instead of 3 MB) compared to the i5s.

    The jump from the 2.4 to the 2.8 is 11 to 13% overall.


    Whether or not it's worth the expense really depends on what you are doing on the machine and your own personal opinion on the value of performance vs. cash in hand.


    If you do a lot of CPU intensive work (video encoding, compiling, large image processing) think about it this way: If a 2.4 could encode a video in 10 minutes, and the 2.8 does it in 9 minutes, is that important to you? If it is, then the upgrade may be worth it.

    Also consider the fact that the 13" uses the Iris 5100 iGPU, and it does seem to perform better on the faster CPU, especially with scaled retina resolutions.
     
  21. T-Bob macrumors 6502

    T-Bob

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    Oct 23, 2013
    #21
    Now that would be of interest to me if there was a fair FPS hit using 2.6 instead of 2.8.
     
  22. AlecMyrddyn macrumors 6502

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    Southern Maine
    #22
    Don't get your hopes up...
     
  23. BeRniTo macrumors newbie

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    Nov 1, 2013
    #23
    I wrote a reply two days ago and the webpage said it needed to be approved by an administrator... still waiting though... maybe it didn't arrive to the admins to be approved? :confused:
     
  24. Tears Apart macrumors 6502a

    Tears Apart

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    Outside Closer
    #24
    Thanks, your post is quite informative.

    Do you think the 25% more L3 cache makes a difference? If so, for which kind of operations?
     
  25. EatingApples macrumors member

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    Mar 8, 2011
    #25
    Why is this whole battery life i5 vs i7 so damn complicated :-( I wish the data would be more conclusive.
     

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