How decide between 13 & 15 inch rMBP based on relative power

Discussion in 'MacBook Pro' started by jennyp, Aug 11, 2015.

  1. jennyp macrumors 6502

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    Oct 27, 2007
    #1
    I want to buy a new MacBook Pro to replace my ageing 2009 model, but I can't decide between the top-spec 13-inch and 15-inch models.

    The screen size seems to be a personal choice, based on lifestyle, and I guess it's something I'm going to have to work out for myself. But display screen size apart, what is the difference between the two? As far as I can see, it seems to be between the different CPU and GPU.

    As far as the CPU is concerned, the 13-inch offers a "3.1GHz Dual-core Intel Core i7, Turbo Boost up to 3.4GHz" while the 15-inch offers a "2.8GHz Quad-core Intel Core i7, Turbo Boost up to 4.0GHz". Is this the crucial difference? If so, is it a big one? In what sort of applications would the 15-inch really outpace the 13-inch? Are there many situations where there would be no discernible difference?

    As far as the GPU is concerned, the 13-inch offers a "Intel Iris Graphics 6100" while the 15-inch offers a "Intel Iris Pro Graphics + AMD Radeon R9 M370X with 2GB GDDR5 memory" I don't know what the difference is here at all, or even what VRAM there is in the 13-inch.

    If I can get the "power" side of things straight, then I can concentrate on the choice between the two screen sizes.
     
  2. zhenya macrumors 603

    zhenya

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    #2
    Basically the two things that the 15" model offers over the 13" is discreet graphics - that AMD Radeon card - and a quad-core processor. The 15" is undoubtedly more powerful, but it takes specific sorts of tasks to be able to take advantage of that extra power. For example, many programs can't or won't take advantage of the extra cores of the 15" processor to do more work in parallel, and the single-core performance of the two processors is not all that different. If you can specify exactly what kinds of work you will be doing with what programs, you can get some good advice as to which is the better choice.
     
  3. dusk007 macrumors 68040

    dusk007

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    #3
    The CPU is faster but it would not show all that much in most office/web usage.
    Iris Pro is about 70% faster than the 6100.
    The M370X is again up to twice as fast in games than Iris Pro. About 60% faster in benchmarks.
     
  4. Samuelsan2001 macrumors 603

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    Oct 24, 2013
    #4
    The differences are massive but unless you tell us what you use a computer for, what apps you use and what you typically expect it to do all at the same time, it's impossible to tell wether this will make any difference for you.
     
  5. unplugme71 macrumors 68030

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    #5
    For me, I would get the model with Iris Pro at minimum. Why? Because if you plan to keep it for 3-5 years and need to run something remotely with graphics on the latest OS it will be the equivalent of a non-Iris by then. So to speak. Nothing worse than not having the graphics capability to do what you need 5 years down the road. The MBP isn't a cheap investment so plan wisely. 8GB is min nowadays too. Even if you are barely using 4GB today.

    The next few years will see leaps in bounds in multi-core/threaded applications. Voice control needs processing power.
     
  6. maflynn Moderator

    maflynn

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    #6
    Agreed, and I'd also add the fact you get a quad core CPU with the 15" MBP, another plus for ensuring longevity. I understand for a number of tasks, a 13" MBP will perform nearly the same as the 15" because its only using a single core, but for those tasks that take advantage of the multiple cores, the 15" MBP blows away the 13"
     
  7. Meister Suspended

    Meister

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  8. jennyp thread starter macrumors 6502

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    #8
    Well my main use will be for writing, which you may think would not need much processing power, but nevertheless I find that opening a number of very large PDFs while having many other apps running needs a fair amount of power. There would be occasional image processing too. But moreover I take the point about successive OSs requiring more and more power as time goes on, and since I'd want to keep this for as many years as possible then maybe playing safe and opting for the more powerful 15 inch would be best.
     
  9. zhenya macrumors 603

    zhenya

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    #9
    In that case, I would go with the 13" unless your primary use will be with it permanently seated at a desk. It's just much more portable with better battery life, and is already way overkill for the uses you state. The 13" Pro is already more powerful than the vast majority of the Windows laptops people use professionally. The 15" is really closer to workstation class.
     
  10. T5BRICK macrumors 604

    T5BRICK

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    #10
    The 13" model will work just fine for you.

    Additionally, I'd suggest skipping the i7 upgrade and sticking with the 2.9GHz i5 CPU. The extra $200 spent on the upgrade only gives you a tiny increase in performance.
     
  11. Samuelsan2001 macrumors 603

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    #11
    I agree wholeheartedly with this, unless you want the real estate, having large PDF's open suggest a larger screen could be good for you but performance wise the 13 inch is more than enough.

    Also if you want an easy way to use multiple windows open them in separate desktops and three finger swipe between them.

    See here

    http://www.howtogeek.com/180677/mission-control-101-how-to-use-multiple-desktops-on-a-mac/
     
  12. jennyp thread starter macrumors 6502

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    #12
    Well, OK, maybe the 13 inch then. I suppose it would be OK to use with my 2011 27-inch iMac in target display mode?
     
  13. snaky69 macrumors 603

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    #13
    What would be your typical usage scenario?

    The 15" runs circles around the 13" power wise(it's about twice as powerful), but unless the programs you work with can make use of that power, it doesn't matter.

    Edit: I can't read. Just saw your post. Writing and opening PDFs needs next to zero computing power. The lag you're experiencing is likely due to the slow mechanical hard drive in your older machine combined with possible lack of RAM, not lack of processing power. Either machine would work very well (in fact they would be too powerful) for your needs.
     
  14. jennyp thread starter macrumors 6502

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    #14
    Some of the PDFs are over 130MB in size. The iMac with 16GB RAM opens them, so I guess either of the MBPs will. I guess the 13 inch would do. It's just that I always seem to have too little power somewhere down the line.
     
  15. meyer1131 macrumors regular

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    #15
    I was facing this same dilemma (I have a 2015 rMBP 13" upgraded 16GB Ram and 2015 rMBP 15" base with iris Pro and need to return one ASAP) and I wanted the increase in graphics performance as well as the comfort in knowing I have the quad core processor for "future proofing". Despite the 13 inch being a more portable device with better battery life (ranging around 4-6 hours on 15" and 7-9 on 13") I enjoy the peace of mind knowing that I have a machine that will be able to handle both graphics and performance tasks for years to come. I am still able to use the 15inch on my lap or in my bed or wheverever I need to (though it's a much smoother experience when it is sitting flat on a table). I also enjoyed the extra screen real estate as I multi task often and like to have multiple windows up on my display.
     
  16. Meister Suspended

    Meister

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    #16
    Actually pdf lag is usually caused by the app that is used to view/edit the document. Preview being one of the worst.

    Computing power is irrelevant for pdfs. If she would on the other hand be running out of ram, she would experience a bit more than just lag.
     
  17. Meister Suspended

    Meister

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    #17
    You dont need 16gb ram to open a bunch of pdfs. That's ridicolus overkill.
     
  18. jennyp thread starter macrumors 6502

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    #18
    You can't go higher than 16GB RAM in the 15 inch as far as I know. I think I'll be going for that one anyway.
     
  19. Meister Suspended

    Meister

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    #19
    You should also think about an egpu for extra pdf-action.
     
  20. unplugme71 macrumors 68030

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    #20
    Yes. It will come in handy once apps are ready for multi-core/thread.
     
  21. snaky69 macrumors 603

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    #21
    Agreed on all counts.
     
  22. maflynn Moderator

    maflynn

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    #22
    No question but I will say that even if there is a lack of apps that take advantage of it, you will see an improvement in performance if you run multiple apps at the same time.
     
  23. unplugme71 macrumors 68030

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    #23
    Unless you are encoding/decoding using cpu, chances are, the few ms of cpu time will be minimal on multi-core. I run 1 core in vmware and find that I can do a lot of things. It's ram and disk i/o that are needed with today's tech.

    This is why at work we oversubscribe our CPU 10 to 1.
     
  24. Vikinguy macrumors 6502

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    Sep 19, 2007
    #24
    8 gb of RAM still seems like a TON to me. Wasn't that long ago I bought and HP with 512mb. :)
     
  25. jennyp thread starter macrumors 6502

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    #25
    That's just not the case in my experience. When, for instance, I annotate such large PDFs (by highlighting certain passages etc) on my iMac (3.4 GHz Intel Core i7, 16GB RAM) it takes a fair time for them to be saved to their new state. Perhaps the 15-inch rMBP will cope better.
     

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