MBP Haswell: Performance and battery life impact of faster processor

Discussion in 'MacBook Pro' started by inkyoto, Oct 30, 2013.

  1. inkyoto, Oct 30, 2013
    Last edited: Oct 30, 2013

    inkyoto macrumors regular


    Oct 30, 2013
    I'm looking for information on whether a higher GHz computer will actually get stuff done faster when running in low- and medium-load situations.

    Let's say that I'm browsing the web, watching videos, or doing software development in Xcode. In each of these cases, will a higher GHz computer do these tasks any faster? Does it add up over years? Or does it only add up when doing high-load processing?

    And if it is faster, then what is the impact of that on battery life? Will OS X automatically throttle the CPU when in a battery situation?

    Just trying to decide on 2.3GHz vs. 2.6GHz top-line MBP Haswell, keeping performance and battery life in mind. Tests on pre-Haswell rMBPs seemed to show that the faster processor resulted in a 1.5 hour impact on battery life.

  2. fgravicle macrumors newbie

    Oct 30, 2013
    I am assuming you are talking of processors from the same family where everything else is the same except the system clock. To answer your first question, a higher clocked processor does things at a higher base clock speed. This means the most things like browsing, compiling in Xcode etc are done faster. Frequency and power consumption are linearly proportional so energy consumption increases linearly as clock speeds go up. Which means that the faster processor might consume more energy doing the same task compared with a slower one. Given that modern processors are quite powerful, there is only going to be very little time to be saved from using a slightly faster processor in day-to-day tasks. Intensive jobs like video encoding, Xcode compiling etc might benefit a little more.

    To answer your second question, a higher clocked CPU will hit battery harder. It's heat dissipation is higher as well. While OS X is very good with power management and power-gates the CPU or parts of it which aren't being used. Mostly, the CPUs will have very similar idle power consumption. However, the overall impact on the battery life of the Maxine might be non-trivial.

    The 2.3 GHz CPUs in the rMBPs are very capable and unless you must have a higher clocked machine, I'd suggest spending that money towards 16GB of RAM or a bigger SSD.
  3. Mac.User macrumors 6502

    Aug 25, 2013
    It's a case of:

    3.0 seconds at 2.5v
    2.5 seconds at 2.7v

    Eventually the numbers balance and one is better over time, but it may no be a noticeable change by the time the battery runs out.
  4. Starfyre, Oct 30, 2013
    Last edited: Oct 30, 2013

    Starfyre macrumors 68030


    Nov 7, 2010
    fgravicle put it very nicely.

    If you do code, or do processing tasks, the higher click speed with the 2.6 (300GHz per core for 4 cores in the 15'') does very nicely.

    Because of the speediness, it can result it a quieter overall experience when your using your macbook pro, though at the same time it may generate a little more heat during normal use. On very heavy loads where your running heavy heavy benchmarks for extremely long periods of time, the 2.6 may get hotter than the 2.3 and most definitely consume battery life quicker, but most of the time you shouldn't be hitting it.

    Getting the 2.6 also gives you the best version of Iris Pro that is slightly faster than the 2.3. What this means is if you really really needed battery, but you needed to do some graphics work, you could use an application like gfxCardStatus to disable the dGPU when you need the battery or if you want it to run cooler, and the system will perform better than the rest. In fact users, who do that actually have battery life of at least 8 hours on their 2.6 machines compared to others who don't.

    ~8% difference may not seem like much, but if your planning on keeping it for a while and not upgrade every time a new MBP comes out, having the extra speed is nice. The cost for a 2.6 is not all that big compare to the other upgrades, plus when it comes time to resale, you may be able to differentiate yourself from the crowd of 2.3's.

    So to sum up, 2.6'' would be better than the 2.3 in the following ways:
    - Faster for computationally intensive tasks, coding/compiling, (and VMs)
    - Slightly better integrated graphics, best of Iris Pro
    - Best quad core processor in a laptop to handle the most demanding tasks. If your computer can't handle it, no other laptop can in this day and age. (from the processor standpoint)
    - May be quieter on normal and idle loads due to its speed
    - Less reliance on dedicated card when you want to use your integrated GPU for some tasks

    - Can run hotter and consume more battery especially at high loads
    - On lower and normal loads, can disable dedicated card and can get 8+ hours of battery life (as reported by some owners with the 2.6 15'')

    Cost would be a con, but comparatively, its much cheaper than SSD and RAM upgrades, so even if you had lower resale value in the future... its really the least of your problems. If you live in the US and have a student discount, $180 is nothing compared to the other upgrades you could get.
  5. Quu macrumors 68030


    Apr 2, 2007
    All three chips have the same thermal design power (TDP) of 47 Watts. So it would be nice to see how the energy consumption on the three chips compares based on that Intel is saying they all have the same thermal output.
  6. Starfyre macrumors 68030


    Nov 7, 2010
    Like Apple, they just take one model, figure out its battery life, and apply that to all the models. I have the feeling its the same. Just because the TDP is the same, doesn't entail the processors consuming the same amount of heat. At higher clocks, more heat should be consumed, except for the speed factor, which may reduce the heat on idle and normal loads. Some statistics would be nice... wish they would come soon.
  7. inkyoto thread starter macrumors regular


    Oct 30, 2013
    Hey all, thanks a ton for your help here. It looks like the 2.6 it would make a difference for some of the tasks that I use it for. Since I use my laptop plugged-in most of the time, I think getting the more powerful machine is the best idea here. And when I'm not plugged in, I'm trusting Apple's battery optimization to make the impact not so great.

    Just ordered the CTO 2.6GHz. Whoo!
  8. KevinMHC macrumors member

    Nov 5, 2012
  9. Starfyre macrumors 68030


    Nov 7, 2010
    At some point, when the fastest processor gets at least 8 hours minimum, thats good enough. Sure it could get 8 hours and 45 minutes, but because of the added performance its worth it.

    Based on the review you just posted, copying and decompressing a 6GB Folder is almost twice as fast on the 2.6 vs the 2.4. No idea why compressing is slower than the Early 2013 (maybe a faulty unit?)

    Wish they had something like this for the 15''.

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