iMac 3.6GHz i5 vs 2.8GHz quad i5?

Discussion in 'iMac' started by chowmein, Jul 28, 2010.

  1. chowmein macrumors member

    Feb 20, 2009
    The 3.6GHz BTO option for the low-end 27" is only a dual-core but has hyperthreading while the 2.8GHz in the high-end 27" is a quad-core but doesn't have hyperthreading. Both CPUs can execute four threads at once, but which one's faster??
  2. lyrrad721 macrumors regular

    Jul 28, 2010
  3. emaja macrumors 68000

    May 3, 2005
    Chicago, IL
    It depends on the program. Some programs like hyperthreading while others work better with more physical cores.

    In other threads here, the consensus seems to be that by the time you option up an iMac to include the 3.6GHz i5 that you are very close price-wise to the 2.8GHz quad-core i5. Might as well get the better graphics card and extra VRAM and get the QC i5.

    FWIW, I was looking at the same thing and decided to get the QC, but won't be ordering until next week since I am out of town.
  4. zedsdead macrumors 68040

    Jun 20, 2007
    For most programs right now, the Dual-Core 3.6 will spin circles around the 2.8 Quad, however, that should be changing in the near future.

    Programs such as Handbrake and Compressor can take advantage of the extra cores, which speeds them up a lot. Apple's other programs sadly do not do so right now, but as I said, the next round of software upgrades should address these problems.

    I personally would go with the Quad, because it will get faster once the software catches up with it.
  5. chasingmars macrumors newbie

    Jul 1, 2010
    There are other differences

    The dual core hyperthreaded 3.6 GHz is the i5-680 from all indications. It's a 32nm core (with 45nm unused on package graphics) with a TDP of 73W, while the quad core chip appears to be the i5-760, which is 45nm and is a 95W part. The dual core -680 supports the AES New Instructions, while the quad core -760 does not. VT-d and TXT are also present in the -680 and not the -760, but I think that's less relevant. The -680 has a 1ku price of 294$US while the -760 is much cheaper from intel at $205US, which is interesting.

    Overall, I was looking at the same decision. I went with the 3.6GHz dual, and bumped my graphics up to the higher end option since I was doing BTO anyhow. Price was mostly a wash therefore with the 2.8GHz system. I figured both were more than fast enough for what I needed, and both do 4 threads, but figured in most daily use scenarios, and for the type of things I do that needs clock speed (honestly, mostly games, my real work doesn't need anything like the horsepower of either), the lack of large scale balanced threading means the 3.6 is likely the better real world performance for that. The fact that this gives me a cooler, therefore quieter, computer (a 22W difference is a substantial fraction of the whole iMac power budget) and also the AES extensions for future is just gravy.
  6. TMRaven macrumors 68020


    Nov 5, 2009
    Physical cores will always be better than virtual cores that are emulated through hyper threading. Programs are either multi-threaded or not, so there is no special coding for hyperthreading only. Also note that the quad core lynnfields have considerably high turboboost, and can get up to 3.5-3.6ghz from it while single threaded.

    Getting the 3.6ghz clarkdale is only meant to boost ePenis with the 3.6ghz clock.
  7. aliensporebomb macrumors 68000


    Jun 19, 2005
    Minneapolis, MN, USA, Urth
    Turbo Boost

    Definetely get a processor with the Turbo Boost feature whatever you do....

    Just to give you guys an idea of what the Turbo Boost feature in actual practice works like on a Mac:

    I was running Boinc/SETI @ Home, iTunes, Safari and a few other incidental utilities and this is what Temperature Monitor saw:


    So none of the cores were actually going the "clocked" speed of the processor, they were all going faster.

    And lots of the programs I use are multithreaded so many times I have "eight cores" functioning.
  8. xraydoc macrumors demi-god


    Oct 9, 2005
    But the catch up time for efficient multicore-aware software will still be a couple of years for basic desktop apps. There's no big push to make Word multi-threaded. Given that, and given the fact that the buyer's iMac may be replaced with a new model in 3 years anyway, it may make more sense to go with a higher-clocked dual core than a slower quad-core, though too bad there isn't more of a price benefit.

    For me, I use mutlicore-aware apps (Handbrake, Parallels and Osirix mainly), so the quad i7 was the right choice for me.
  9. Revival Cr8tive macrumors member

    Jan 2, 2009
    This is all really good information... I'm still trying to figure it out though... It seems like there conflicting reports out there.

    Basically all I will use my Mac for will be Website Design in Photoshop CS3 and CS5 in the near future...

    What will be the best option?

    Go for a Maxed out 21.5" or go for a 27" 2.8 Quad Core i5 or i7????

    Need to make a choice soon!

    Help Please!!!
  10. mattd313 macrumors newbie

    Jul 13, 2010
    I'm in your boat. I've decided to go with at least the quad 2.8 core i5.
    I mainly use it for Photoshop and Illustrator, but on occasion (and perhaps soon more often) use iMovie, Adobe Premiere, as well as HandBrake.
    I get off work in 30 minutes and plan to go pick up the 2.8 core i5.
    I don't see anything convincing me I should get a core i7. Though it is faster, for me I won't see it often.
  11. diegobgr macrumors 6502

    Nov 22, 2009
    It's too easy.

    If you can work with a 27" screen or if you are enconding video, go for i7.

    If you need to be 21,5" due to space, just go i5 3.60 Ghz. I think that the i5 upgrade can help in the future.

    Get sure about size.

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