Classic Question: i7 or i5?

Discussion in 'iMac' started by Josh Kahane, Dec 27, 2010.

  1. Josh Kahane macrumors 6502

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    #1
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    Hi

    Sorry, the classic question returns. It's really hard deciding as it seems fairly split everywhere I look.

    I am getting a new 27" iMac tomorrow and have enough money to get the i7 however to save £160 would be great! Is it reAlly worth the i7?

    I will be using my computer everyday, heavy usage. Plenty of email, web browsing but also a couple of games now and again with some Photoshop and Xcode in there.

    Thoughts? Or rather than saving it, better thing to spend £160 ish on when getting my iMac? I believe that $200 for those in the USA.

    Thanks.
     
  2. TMRaven macrumors 68020

    TMRaven

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    Nov 5, 2009
    #2
    The i7's hyperthreading will possibly help for futureproofing 3-5 years down the line, but it wouldn't make the biggest of differences with your workload.

    Your call (I'm a believer in spending the most you can afford for computers)
     
  3. Shylad macrumors newbie

    Shylad

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    Dec 1, 2009
    #3
    Hi, I had the same question a few months back, I ended up getting the i5 and spent the £160 on an external hard drive. I have Adobe CS5 Master Collection and haven't had any issues running any of the programmes in it. I also play Warcraft and it runs great so spending the £160 on the i7 would have been a waste of money for me.

    Simon.
     
  4. iMacN00b macrumors member

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    Sep 9, 2010
    #4
    I have the i7 and the only time I manage to max out the cores is video encoding under windows. (Microsoft Expression)

    New games are now mostly optimized for 3-4 cores, & by the time they can finally use hyperthreading down the line the ATI 5850 Mobility won't be able to run much past 720p anyway.

    Unless you are big into Film encoding or other major CPU heavy tasks, I suggest you save the cash and get the i5.
     
  5. mpe macrumors regular

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    Sep 3, 2010
    #5
    Unless you encode video or do scientific calculations all the times ignore i7. Rather spend your money on SSD. This will multiply performance of your computer in pretty much everything important. Hyperthreading and increased frequency of i7 shines in synthetic benchmarks but you will never notice that when using your computer. Or would you care if your video is encoded in 12:21mins or 2 minutes later?
     
  6. mpe macrumors regular

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    Sep 3, 2010
    #6
    I don't think so. Look back. 5 years ago we had Imacs G5 and people were deciding between 1.6 or 1.8 GHz G5s. Would you be happier now to have 1.8 instead of 1.6?. Both CPUs are obsolete now and their performance is almost the same for todays apps. The same will apply for i5 for i7. Perhaps there will be difference between dual-cores and quad-cores but certainly not between standard quad-cores and tuned quad-cores.
     
  7. TMRaven macrumors 68020

    TMRaven

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    #7
    Apples to oranges. I personally don’t believe you can compare a 11% increase in clock speed on a completely different cpu architecture with a virtual doubling of threads from 4 to 8 on intel cpus that provides upwards of 20-30% increase in performance when all 8 threads are utilized to their fullest over just 4 threads, along with the slight increase in clock speed. On a more appropriate note however, I can definitely feel a difference between 2.66ghz and 2.0ghz core2duo when it comes to multitasking on the computers at my university, and that is more along the lines of a 20-30% increase in performance. Your argument is valid however, and it’s the reason many users of the current macbook pros choose to go i5 arrandale over i7 arrandale, because the i7 only offers a clock increase. I would love to have an SSD in my iMac, but I’ll wait until they’re down in price and offer cost per memory that’s close enough to today’s hard drives.
     
  8. BulletToothTony macrumors 6502

    BulletToothTony

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    Jan 5, 2009
    #8
    i have owned over 5 iMacs over the last 2 years.. and every time i got a new one i regreted not getting what i REALLY wanted.. FINALLY after selling them and saving little by little i was able to buy my i7 and finally i'm truly satisfied with my purchase.

    Think about that and what you REALLY want.. don't take advantage of the i7 85% of the time but when i do OMG it feels so good to see you computer just fly thru some video encoding.

    Do what you REALLY want. Best advise i can give you.

    Plus you can wait a month or two before you really need an external hdd.
     
  9. squirrelking101 macrumors newbie

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    Dec 26, 2010
    Location:
    Maine
    #9
    Is the i5 quad-core like the i7 of the iMac is? When I am on the website, I see i5 but can't find definitive information on quad-core availability. Although in the refurbished section there are clear indicators of quad-core within the title name. Are there dual-core i5's?
     
  10. TMRaven macrumors 68020

    TMRaven

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    #10
    There is a dual core i5 offered for the iMac, but it's the clarkdale that is clocked at 3.6ghz.

    The quad cores in the iMacs are the lynnfields.
     
  11. mpe macrumors regular

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    Sep 3, 2010
    #11
    I don't know what multitasking apps you run on your computer, but at least on mine CPU cores are idle most of the time. Even during moderate use (surfing the web, editing photos, listening music, downloading files, etc.). The only time CPU is used and become bottleneck is when I export slideshow in Lightroom to 1080p video. Another example is batch conversion/imports in Lightroom. Basically these kind of tasks that take longer. But these are not activities you do every day. In basic interactive tasks you will never notice if you run i3, i5 or i7 CPU unless they utilize CPU much (and they almost never do). All these modern CPUs are very fast and provide exactly same "interactive speed".

    On the other hand, upgrading standard HD by SSD means performance can be immediately seen. I can guarantee you that you will notice if your application opens in milliseconds instead of seconds, if you boot time is three or more times shorter, if you can instantly open ans save your file without waiting for disk, etc. It is dramatic difference nothing like 20% - it is magnitude faster.
     
  12. zedsdead macrumors 68040

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    Jun 20, 2007
    #12
    This is the truth. My fastest Mac is my Macbook Air when it comes to everyday use. The Flash Drive is even faster than the SSD that was in my Macbook Pro. I agree that you should get an SSD over a faster processor, unless you plan to do a lot of video encoding or something that you know will take advantage of the added cores. Most apps (especially Apple's) are sadly not written to take advantage of more than one or two cores.

    Now if you plan on using Handbrake or Compressor, then the i7 will be used well.
     
  13. TMRaven macrumors 68020

    TMRaven

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    #13
    But aren't we talking about future-proofing 4-5 years down the line here? You opened your argument by stating after 5 years the 1.6ghz and 1.8ghz G5s were both too slow for the average user to notice any difference in performance or headroom when doing computing tasks today. So with that argument, why would you talk as if there's little justice to get an i7 because the average user sees little performance increase or headroom for today? That is why we're comparing the difference between the clock speed increase between the i5 and i7 arrandales versus the cock speed increase and doubling of threads between i5 and i7 lynnfields. Almost no application today is coded to take advantage of more than 2 threads (and even then, the ones that do-- like handbrake-- only do so in a broad sense that isn't of the utmost efficiency, so there's still wasted resources) So there's plenty of headroom for the usage of all the power and threads an i7 could bring 5 years down the line I feel.

    Also with the logic behind that argument is that I should just go out and buy a core2duo iMac because I won't notice the difference for everyday tasks, and the ones that do utilize a lot of cpu resources are few and far between and take time anyways?
     
  14. mpe macrumors regular

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    Sep 3, 2010
    #14
    Did you try to realize why some applications can't utilize all the good of multi-core CPUs? Some apps just don't need or can't be written in a way to use more that 1-2 threads. There are even type of tasks that runs better when executed in one thread and there is no point in optimizing them to more threads (it might just add overhead and memory).

    It is true that there are apps that could be optimized better for multi-core CPUs. Any such optimization would make also quad-core i5 to run better. Hyper-threading is just a smart way how to utilize existing cores effectively. On the other hand it is not true that there is some hidden potential that will make the difference between quad-core i5 and i7 significant enough to consider i7 as more future proof. It will always be like +30% in the very best case - not enough to make your purchase future proof in 3-5 years from now. I would say 3x-10x better performance could make your purchase more future proof but not 30%.

    Well, the choice was between quad-core i5 and i7. But still I am pretty sure that 2009 Core2duo 3.06 iMac with SSD option (I don't know from head if there was such BTO option) gives in many standard apps much better computing experience than top end i7 with conventional HD. Now or in 3 years from now. Unless all you do is Handbrake or contributing to folding@home.
     
  15. TMay macrumors 68000

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    #15
    I'm primed for Sandy Bridge, as I can really use the AVX processing for my engineering software, and the multiprocessors for rendering, but the downside is that I will have to wait until fall to see a Xeon version in the Mac Pro. On the other hand, I might be perfectly happy purchasing an iMac at the Sandy Bridge upgrade and getting by with that until the Mac Pro comes out. The Mac Pro will ultimately host all of my current Windows software, replacing a PC, so I won't mind having the iMac handy for general use.

    What's your guess on when Sandy Bridge makes it into the Mac Book Pro and iMac?
     
  16. aliensporebomb macrumors 68000

    aliensporebomb

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    #16
    I dunno....

    I've got my i7 running 100% with all "eight" cores pegged.

    I have BOINC/Seti at home on there and a number of other apps that utilize "more than four".

    I'm happy with it. Your mileage may vary.
     
  17. biggd macrumors 6502

    biggd

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    #17

    +1
     
  18. mpe, Dec 31, 2010
    Last edited: Dec 31, 2010

    mpe macrumors regular

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    #18
    I think that you overrate importance of Hyper-threading.

    Despite of view of many and Intel marketing, hyper-threaded i7 CPU can't execute eight threads at the same time. It can still execute four (each on every core) as there are just as many execution units as on non hyper-threaded CPU (like i5). Hyper-threaded CPU just adds some extra hardware (like instruction pointer and other CPU state registers) to allow for more efficient transition to another thread when the first one is idle for whatever reason. To the operation system it appears as twice as much CPU cores but physically these cores are not there and just one thread is running on each core at the time.

    Should the multi-threaded software be ultimately optimized (instruction are ordered in a way to have minimum or no idles in the instruction flow by some clever compiler in the future) the hyper-threading would even have no performance benefit. Also there is no guarantee that app that spawns 8 threads will automatically run faster on quad-core hyper-threaded CPU than on normal quad-core. It always depends how the application is written and where is its bottleneck.

    For certain tasks hyper-threading gives decent performance bonus, on the other hand for others there is no benefit at all or even performance drop (due to cache trashing and CPU affinity overhead, increased memory requirements for heavily multi-threaded app, etc). Fortunately, i7 is almost never slower than i5 due to faster clock and more aggressive turbo boost multipliers. But it is wrong to see hyper-threading as some fundamental quality difference between i5 and i7 that will magically make future application fly. d
     
  19. Hellhammer Moderator

    Hellhammer

    Staff Member

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    #19
    Since nobody has done it yet, HERE are some benchmarks comparing the i5 and i7. Simply put, i7 is faster in some encoding, rendering and compression tasks. If OP is not going to do stuff like that, then the difference between i5 and i7 would be fairly negligible for him.

    However, spending 160£ now will be payed back if/when OP is going to sell it. The money won't be wasted
     
  20. edtate macrumors newbie

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    Oct 1, 2010
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    Tempe, AZ
    #20
    Save yourself the headache and get a refurb i7. Costs less than a new i5 and still has the full manufacturer's warranty *plus* all the performance boosts and everything other people have so nicely linked in previous posts. There's no difference between my refurb and a new i7 coming out of the apple store today, other than the fact it can be called a refurb. And like I said, it still comes with the same exact warranty you'll find with a brand new comp and you're still able to buy the apple care package also.
    I've personally had mine for 3 months and has worked like a charm; I absolutely recommend you look into this route.
     
  21. tbayrgs macrumors 603

    tbayrgs

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    #21
    Best advice yet.
     
  22. PracticalMac macrumors 68030

    PracticalMac

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    #22
    Would rather use the money for a backup drive, but some good advice.
     
  23. Maddox macrumors newbie

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    Jan 5, 2011
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    USA
    #23
    Hi!
    i5 = DMI controller = 2 GB/s
    i7 = QPI controller = 25.6 GB/s
    There is a huge difference in bandwidth. The only difference here is that the i5 CPUs will have 16 integrated PCI-E 2.0 lanes, meaning really low latency between the CPU and GPU/expansion cards. This will compensate for the lack of bandwidth.....
     
  24. Hellhammer Moderator

    Hellhammer

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    #24
    That would be the case if iMac used i7-9xx "Bloomfield" series. However, iMacs use i7-8xx "Lynnfield" which uses the same LGA 1156 as i5 and thus DMI
     
  25. aCondor macrumors 6502

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    Oct 20, 2010
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    United States
    #25
    You'll be fine with the i5. Depends how long you want to future-proof your computer. i7 may add a couple years to its lifespan.
     

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