2011 27" iMac - i5 vs i7

Discussion in 'iMac' started by nightfly13, Jun 12, 2011.

  1. nightfly13 macrumors 6502a

    nightfly13

    Joined:
    Jul 17, 2008
    Location:
    Ranchi, India
    #1
    I see myself slipping higher and higher in my iMac choice. I'm a screen real estate snob so I want the 27" (to go with my 30") and I think I need the upper-end 27" since I'll be running 3 screens (27" in-built, 30", and a 720p projector) and 512mb on the base 27" would be insufficient. I'm not a big gamer, but trying to run over 8 million pixels on 3 displays from a single 512mb GPU seems short-sighted.

    So that brings me to the $1999 iMac. My next question is about CPU choice. Some cross-referencing on Newegg suggests that both the 3.1ghz i5 and the 3.4ghz i7 are rated at 95w. I can't confirm it right now, but I believe the lower end 27's 2.7ghz i5 is rated at 65w. Power consumption is actually a big deal to me, and if I could get away with the GPU then I'd stick with the entry-level 27".

    Assuming I'm 'stuck' with a 95w CPU due to video card needs, is the 'hyperthreading' functionality of the i7 (and marginal clock increase) worth $200? I do a lot of compressing/decompressing (rars, parity checks, etc) that use all 4 cores of my current machine (or 2 cores in my laptop) and some video encoding (making videos friendly for iOS) but don't need the power really for every-day workflow. Do the virtual 'cores' provided by hyper-threading give me considerably faster compression/decompression times?

    My other reasoning is that the i7 vs i5 branding will fetch a decent premium when it's time to re-sell this (in 3-4y).
     
  2. nightfly13 thread starter macrumors 6502a

    nightfly13

    Joined:
    Jul 17, 2008
    Location:
    Ranchi, India
    #2
    155 views and no responses. I guess I hit too many topics in one massive post.

    Two main questions:

    1) the 512MB 6770M is going to struggle to run a 27" iMac, external 2560x1600 30" and a 720p Projector, right? More worried about exposé smoothness and HD playback than gaming frame rate.

    2) Compressing/Decompressing is going to be considerably faster with a hyper-threading-enabled i7 than the merely quad-core i5?

    Thanks.
     
  3. elithrar macrumors 6502

    elithrar

    Joined:
    May 31, 2007
    #3
    It'd be fine for Expose and HD video playback, but gaming is a no-go at native resolution with the 6770M. It simply isn't powerful enough.

    Yes. Definitely.
     
  4. Bear macrumors G3

    Joined:
    Jul 23, 2002
    Location:
    Sol III - Terra
    #4
    It actually depend on what software you run. However, I'd say if you wind up going for the higher end iMac and money isn't that much of an issue, it can't hurt to go for the 2GB VRAM upgrade.

    For what you list in your posts, the i7 would definitely show speed improvements. The question is... how much of your time is spent on compressing/decompressing stuff? Is the upgrade wort it to you time wise?

    On the other side of the coin, spending a little more money on the machine now may mean that it will last you another year or longer before it feels too slow and needs replacement. It's a tough call sometimes on how much of a machine you need and how long it might last you.
     
  5. VulchR macrumors 68020

    VulchR

    Joined:
    Jun 8, 2009
    Location:
    Scotland
    #5
    I'm also considering the i7 27" - can anybody provide information about how well the new iMacs dissipate heat? There's no sense in getting top of the line if it cooks the components.
     
  6. omvs macrumors 6502

    Joined:
    May 15, 2011
    #6
    I don't have the i7 version, but my 27" 3.1GHz i5 w/ 6970 2GB seems to dissipate heat fairly well, even when I'm abusing it for hours. The top edge of the machine will get a bit hot, but the fans still don't spin up very fast (~1500RPM is the top i've seen), and the temperature readouts seem very acceptable. Its nice having a machine that doesn't get too loud unlike my old mini-tower PC.

    If you really care about squeezing every once of performance, the i7 gives you a ~10% frequency bump, and thats probably enough to justify the cost. Personally I'm still undecided on hyper-threading & virtual cores, though at least its better than it was in the P4 days when half the time you'd see a speed decrease. :(
     
  7. nightfly13 thread starter macrumors 6502a

    nightfly13

    Joined:
    Jul 17, 2008
    Location:
    Ranchi, India
    #7
    Any idea if the i7's 8 threads show up individually as CPUs?

    This is a bit of a petty question, but I use menumeters to monitor CPU activity. I was gratified going to my first dual core machine, then again to my 2xdual core Mac Pro now showing 4 CPUs. Will the i7 show up as 8? I know only multi-thread aware apps will utilize all 8 but it'd be cool to see.

    What's the difference between apps being multi-core aware vs mutt-thread aware? Examples?
     
  8. NutsNGum macrumors 68030

    NutsNGum

    Joined:
    Jul 30, 2010
    Location:
    Glasgow, Scotland
    #8
    In Activity Monitor you will see 8 active "cores" on the i7.
     
  9. Nanker/Phelge macrumors regular

    Joined:
    Dec 6, 2010
    #9
    In iStat Menus the i7 shows up as 8 indivudial cores. Until you start using processor heavy applications that kick in the HyperThreading you will only see every other core active (#'s 1,3,5,7)
     
  10. nightfly13 thread starter macrumors 6502a

    nightfly13

    Joined:
    Jul 17, 2008
    Location:
    Ranchi, India
    #10
    Fantastic - thanks everyone for the feedback. 27" i7 it is!
     
  11. neroroxxx macrumors newbie

    Joined:
    Sep 23, 2010
    #11
    I just bought the highest 27" iMac, spent a good $2,600 on it, im not rich by any means but after owning macs for the past few years i decided i needed to go for the best of the best and suck it up, i got the i7, 2Tb and 2GB video card since i'll be working on video editing and i'm a graphic designer and web developer constantly working on illustrator, dreamweaver and dashcode, the only thing that sucks is how long it's going to take for me to get it! arrives between july 1st and 6th, ugh!
     
  12. nightfly13 thread starter macrumors 6502a

    nightfly13

    Joined:
    Jul 17, 2008
    Location:
    Ranchi, India
    #12
    i7 is often available in Apple retail stores..

    FWIW, I called 3 Apple retail stores and all 3 had the same model in stock: 27" i7 w/ 1TB and 1GB gpu. Seems to be the common non-stock model they carry.
     

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