Speed difference between i5 and i7

Discussion in 'iMac' started by c073186, Oct 24, 2015.

  1. c073186 macrumors 6502a

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    Nov 2, 2007
    #1
    I'm going to be purchasing the new 27-inch Retina iMac just released, and am trying to decide between the i5 and i7. I'm wondering how much of a noticeable speed difference there would be between these two. For day to day tasks like iTunes, Photos, Office... would there be any difference in terms of how quickly apps start and overall responsiveness?
     
  2. joema2 macrumors 65816

    joema2

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    Sep 3, 2013
    #2
    No major difference for those scenarios, and possibly not even noticeable in a blind test.
     
  3. Spink10 macrumors 601

    Spink10

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  4. firewire9000 macrumors regular

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    Sep 15, 2015
    #4
    For those uses choose the i5, is totally enough. I will recommend i7 only for those who work on multimedia, specially audio production.
     
  5. huffy15 macrumors regular

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    Montreal, Canada
    #5
    hyperthreading, hyperthreading, hyperthreading
     
  6. joema2 macrumors 65816

    joema2

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    Sep 3, 2013
    #6
    If anyone with an i7 Mac thinks hyperthreading might make a difference in their workload, they can use the CPUSetter utility, turn hyperthreading on/off, and run their own tests: http://www.whatroute.net/cpusetter.html

    I have tested workloads with this utility many times and it seems safe but use at your own risk.

    In general hyperthreading helps a narrow range of multithreaded workloads. It improves FCP X encoding by about 30% but does not appreciably improve Lightroom import, preview generation and export.
     
  7. ohsnaphappy macrumors regular

    ohsnaphappy

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    Jan 14, 2013
    #7
    But it kicks butt in the develop module!
     
  8. magbarn macrumors 68000

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    Oct 25, 2008
    #8
    If you edit media files for a living the i7 is a necessity.
     
  9. dumastudetto macrumors 68020

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    Aug 28, 2013
    #9
    I always recommend everyone goes for the i7 because it offers incredible performance over the i5 and guarantees a longer life for your machine. Do not go for the cheap option you'll regret it forever basically.
     
  10. huffy15 macrumors regular

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    Jan 6, 2009
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    #10
    Hyperthreading is very awesome when you're running multiple vagrant or vm. That's the only thing I'll regret on my i5. I do the math and it would cost me an extra 500$ for the i7. I'll stay with digital ocean or build my self a cheap pc.
     
  11. c073186 thread starter macrumors 6502a

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    #11
    Would there be any noticeable difference in noise or heat output in an iMac using i7 compared to i5?
     
  12. cincygolfgrrl macrumors 6502

    cincygolfgrrl

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    #12
    i7 here. I do similar tasks to what you're proposing. The only times I've heard fans are when using Handbrake to encode videos. The i5 would do that too. If money is an issue, get the i5. Your only problem will probably be chip envy.
     
  13. iMas70 macrumors 6502a

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    MA
    #13
    I'm flipping a coin to decide this now. I usually go for the most power that I can get. Sometimes I don't need it but I rather have it just in case. I don't think I'd give an i7 much of a workout though. I only use my computer for e-mail, internet, basic functions, photo storage and just a little editing. The i5 probably won't work up a sweat with this but as cincygolfgrrl said, "chip envy" :)
     
  14. cynics macrumors G3

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    Jan 8, 2012
    #14
    I can't speak for Skylake but the i5 Haswell can't get hot enough to get the fan off its 1200 RPM idle speed. That said the i7 is faster, more work more heat.

    I use Handbrake daily, and yes I agree you will get chip envy....I have an i5 lol...

    Next go around and I'll get the i7 since I use handbrake so much.

    ...

    OP for the task you listed you won't notice a difference. I do that stuff while running handbrake (so the CPU is running at 100%) and can't barely notice it. So from an idle CPU it's virtually impossible to notice which CPU is in the machine.
     
  15. whodatrr macrumors 6502a

    whodatrr

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    Jan 12, 2004
    #15
    For me, it's not so much about making a particular app run faster. It's about being able to run a power-hungry app in the background (eg. handbrake) while you're doing something else important in the foreground.

    Also, this i7 bump gives you a faster clock (3.3 vs 4.0) in addition to hypertheads, which might be useful? That's about a 20% clock bump....
     
  16. Dirtyharry50 macrumors 68000

    Dirtyharry50

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    #16
    That's really not correct. The i7 is only useful when you are running apps that take substantial advantage of the hyperthreading it offers. If you are not running apps that benefit directly from that you are not gaining any appreciable benefit for the money spent. As mentioned previously above, there are certain apps that benefit but most everyday apps do not benefit from an i7 at all and most games do not either.

    Before spending the money, one should identify what their chosen apps and possibly games can truly make use of before blowing the money just because it is running at a slightly faster clock speed.

    I use quite a lot of different software and i also enjoy gaming both on the Mac and the Windows side via bootcamp on my iMac 27" and I went with the i5 which I have zero regrets about. This is the late-2013 system I own and it is only now I am starting to see a very few games that would actually benefit somewhat from an i7. I have yet to encounter any game requiring one although maybe some do. I haven't seen one on Steam myself that I was interested in at least.

    So I am just one example of a user for whom the i7 upgrade would have been a complete waste of money. When I replace this system I will evaluate then whether or not I feel it is worthwhile. It might be by then for my purposes but it also might not be unless I see a lot of AAA games requiring one or benefitting substantially from one and that is unlikely during the lifetime of the current console generation I would say.

    For the needs the OP posted an i5 would be just fine. All other discussion about unrelated apps they did not mention is moot.
     
  17. Dirtyharry50 macrumors 68000

    Dirtyharry50

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    #17
    Sorry, I should have responded to you directly first. The answer is no. It would not make any noticeable difference at all in the scenario you describe. I run all kinds of stuff and often have a variety of apps open at the same time and on top of that i sometimes I have a virtual machine utilizing two cores in the background and it still is responsive for everyday apps multitasking. In my case I have an older iMac with a 3.4 i5 which has turbo boost to some higher value I forget now and to be honest don't care about. It's not like I don't value decent performance either. I certainly do. I just don't agree with throwing money away on features or capability that I don't actually have use for currently.
     
  18. G.McGilli macrumors regular

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    Oct 19, 2015
    #18
    I'm not trying to go off topic -

    But for example - Logic Pro X - how do you find out if it would use the hyper threading? The tech specs page for the software doesn't even list any minimum processor needed:

    http://www.apple.com/ca/logic-pro/specs/

    And looking at other software too - I don't see this info usually... Is there a list somewhere that let's you know if an i7 would be better suited to particular software?

    I'm leaning towards the i7 since 90% of my work is in Logic and Aperture so I figured the i7 would be more suited to my work.
    (RAW images and audio tracks with 16 simultaneous tracks)
     
  19. ChrisA macrumors G4

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    #19
    For general use like that even the i5 spends most of it's time idle. Fo loading apps fast you want a fast storage device like an SSD not a fast CPU.

    If you were editing video or even audio and still images then the I7 might help but for your use a faster storage is what you want. That said the i7 can't hurt and will make it go very slightly faster
     
  20. ChrisA macrumors G4

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    Redondo Beach, California
    #20
    The above works only if you have an unlimited budget. But if you have some limit then you have to decide if you should spend more for the i7 or if that money is not better spent of more RAN or a faster disk or on an SSD.

    A good analogy is engine size in a car. If the goal is to get to work by 8:30 will getting the bigger V8 get yo there any faster? Not if the freeway always moves at 40 MPH. All that horse power is not used. In a computer used for email, web and word processing most of the time the CPU is waiting for YOU or the DISK. A faster CPU would still wait.

    Some tasks are CPU bound. Rendering video is like that, you start it up then wait 15 or 90 minutes. If that is what you do all day get a Mac Pro.
     
  21. Chippy99 macrumors 6502a

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    Apr 28, 2012
    #21
    Totally agree.

    The general responsiveness of a system is only in part influenced by the CPU in any event. Look at how much quicker *any* computer feels when it's running off an SSD rather than a hard disk, irrespective of what the CPU is. It boots faster, applications load quicker, content loads faster, the whole thing just feels faster.

    For what the OP wants, whether it's an i5 or i7 would make no discernable difference whatsoever.
     
  22. Gav2k macrumors G3

    Gav2k

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    #22
    Are you using a nightly build of handbrake?
     
  23. Dirtyharry50 macrumors 68000

    Dirtyharry50

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    #23
    Particularly where your interest seems to lie primarily with those two apps if it was me I would just contact Apple directly and ask them. Why not go right to the source? From comments around here I'd be inclined to believe they may benefit from an i7 but I'd want to verify that with whoever is making the software in question myself before spending the money unless requirements are clearly stated where it is sold and they always should be but I know that is not always the case.
     
  24. joema2 macrumors 65816

    joema2

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    Sep 3, 2013
    #24


    Apps do not use hyperthreading directly. There is no API for this like there is for GPU access. If apps are multithreaded, and if multiple threads are in a runnable state (not blocked on I/O, a synchronization event, etc) those threads may be scheduled on all available cores. Whether they run on all logical cores on a hyperthreaded CPU or just every other core is a decision of the OS X thread dispatcher. There are cases where running on every logical core hurts performance, e.g, if two threads on the same hyperthreaded core causes "cache thrashing". The dispatcher tries to detect and avoid this. You can see these cases when iStat Menus or other monitoring apps show every other logical core of a hyperthreaded CPU is idle.

    Unfortunately it's difficult for users to know ahead of time these cases. It could vary based on different versions of the OS X thread dispatcher, compiler characteristics, etc. The only reliable method is test and observe and that's only meaningful for the exact hardware/software/OS version.

    Even if it uses all logical cores this doesn't mean it is vastly faster. E.g, going from 4 to 8 logical cores might
    superficially appear to increase from 400% to 800% CPU utilization (as OS X measures it). However this might increase performance by 30%, not double performance. In many cases there will be little to no benefit.

    Why design hyperthreaded CPUs at all? Because the transistor cost is quite limited relative to the potential performance benefit. Under optimal conditions it might give 30-35% benefit, at far less cost than adding physical cores. The IBM Power8 CPU uses 8-way hyperthreading, so each core can run up to 8 threads. However there's diminishing returns from this so Intel's decision to run two threads per core is seeking the most gain from the least cost.
     
  25. G.McGilli macrumors regular

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    Oct 19, 2015
    #25
    Thank you Joema2 for that - I guess then - at the very least (in my case) I would be getting 4.0GHz speed (the i7 option) as opposed to 3.3GHz speed (the i5 option) - as well as the chance that in the future more apps will use the hyper threading effectively etc (I tend to keep macs 5-6 years).

    This entire thread has been helpful, thanks everyone who's helped me out.
     

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