CPU choice - 3.3 i5 vs 4.0 i7 for Lightroom/Photoshop

Discussion in 'iMac' started by eoren1, Oct 21, 2015.

  1. eoren1 macrumors 6502

    Aug 17, 2007
    I'm just about set to purchase the high end retina 27" iMac to replace my current 2011 model. Just stuck on the CPU choice. I get that LR previews will max the CPU. The 3.3 GHz i5 turboboosts to 3.9GHz whereas the i7 idles at 4.0 and boosts to 4.2. Is there something else about the i7 that makes it a better choice than the i5 for a photography workflow?

    Rest of specs will be:
    m395 (don't game ever and think this will be sufficient for my use)
    512GB SSD
    Stock RAM


  2. dark_skies macrumors newbie


    Oct 17, 2015
    Champaign-Urbana, IL
    Lightroom is GPU-accelerated, so hopefully it will make use of your R9 M390 card (their web page seems to indicate AMD R9s are compatible: https://helpx.adobe.com/lightroom/kb/lightroom-gpu-faq.html)
    See also: https://forums.adobe.com/thread/1828580
    Sure the m395X is out of the question?

    Whether i7 is better than i5 -- my quick check showed mixed results. Having lots of RAM seemed to be a big point. https://forums.adobe.com/thread/1828580
    You might want to ask on a Lightroom forum to check more recent findings.
  3. Sirmausalot macrumors 6502a


    Sep 1, 2007
    i7 is great for programs that need multi-treading. Video compression and some high end audio production.
  4. merkinmuffley macrumors 6502a

    Dec 3, 2010
    I doubt you'd notice much difference in those processor choices. Memory is important, add some from one of the 3rd party sellers after you get the system. Not sure which IMac you're getting, but if it's the just announced ones read up on that DCI-P3 color space. DCI-P3 is skewed differently than Srgb in the CIE color model and extends more into the reds and a different set of greens. If you're shooting for cinematography all is good, if you're shooting stills be careful.
  5. eoren1 thread starter macrumors 6502

    Aug 17, 2007
    Thanks everyone

    I'm trying to figure out if I could/should reuse the 4x8gb 1333MHz c9 ram from the 2011 iMac.

    Also planning on getting the new Dell 27" UP2716d I think that covers 100% of aRGB
  6. netnothing macrumors 68040


    Mar 13, 2007
    I'm in a similar situation as you.....do mostly development work with photoshop (large multilayered files) and some video.

    I've pretty much convinced myself to get the i7.

    Where I'm stuck is the GPU. m390 vs m395 vs m395x

    I do ZERO gaming. So I'm just looking for the best card to future proof and get the best benefits mainly from Adobe products.

  7. joema2 macrumors 68000


    Sep 3, 2013

    The i7 is hyperthreaded but in my tests this makes minimal difference on LR 6 import, preview generation and export. I turned hyperthreading on/off with the CPUSetter utility, so tested on the same machine and same configuration.

    Hyperthreading can make a 30% improvement in FCP X export but it doesn't currently help much for LR.

    However the 4Ghz CPU is 21% faster than the 3.3Ghz, so that by itself is a significant improvement.
  8. Moriske macrumors member

    Oct 19, 2015
    You do still have to mention the turbo boost with it 3,3-GHz quad-core Intel Core i5, Turbo Boost up to 3,9 GHz

    If you take this into account, the difference is minimal
  9. ohsnaphappy macrumors regular


    Jan 14, 2013
    The develop module in LR continuously uses all four cores of the i7 AND all four virtual cores of the i7. This is due to the i7's hyperthreading. Hyperthreading gives you four virtual cores in addition to four physical cores. The i5 does not have hyperthreading and thus doesn't have four virtual cores. This is one of the main advantages of the i7 for LR work. In addition, at 4ghz, the i7 has a higher clock speed - which is the single most important factor for LR performance: clock speed.

    Anyone who doesn't believe me about hyperthreading in the develop module can download an activity monitor from the App Store and watch the activity of all "8 cores"

    However, I'm not aware of more than one core working during import and export. I could be wrong. The only place I tested for hyperthreading in Lightroom was the develop module.

    Concerning the GPU, LR6 was the first and only version of LR to employ the GPU. But after LR6 was announced, Adobe published an article stating that GPU performance in LR would ONLY benefit users with high resolution screens, such as the retina iMac. So if you have a high resolution screen, in theory, the GPU will speed up the develop module in LR6.
  10. Moriske macrumors member

    Oct 19, 2015
    Thanks for the clear explanation.

    As for the GPU, I think the differences between M390 and M395 are very small and you should rather think of the M395x
  11. eoren1 thread starter macrumors 6502

    Aug 17, 2007
    Thanks again everyone - incredibly helpful advice

    Kevin, when I priced out the mid vs top end machines and included my desired 512GB SSD, the difference was only $100 for the 'better' 395 vs 390 card and the faster i5 CPU. It became a no-brainer for me to go with the top end at that point.

    Ohsnaphappy, thanks for the thoughts on i7. Forgot about hyperthreading being exclusive to the i7. One of my thoughts was that the i5 would draw less power at 'baseline' and possibly run cooler than the i7 while still having some headroom to ramp up to 3.9.

    Still not convinced the 395x offers me very much but, of course, very few have taken ownership of an i7/395x retina P3 yet...
  12. Moriske macrumors member

    Oct 19, 2015
    During a visit to the Apple store I clearly informed me and the difference between a M390en M395 is for the extra expense just too small, right?
  13. eoren1 thread starter macrumors 6502

    Aug 17, 2007
    27" iMac (mid) - 3.2 i5/8ram/512ssd/m390/trackpad - $2449
    27" iMac (mid) - 4.0 i7/8ram/512ssd/m390/trackpad - $2749
    27" iMac (top) - 3.3 i5/8ram/512ssd/m395/trackpad - $2549
    27" iMac (top) - 4.0 i7/8ram/512ssd/m395/trackpad - $2799

    The difference between 390 and 395 when going with i5 is $100 but you end up with a better i5
    Difference is $50 when upgrade to i7
    *This assumes you go with the 512gb SSD which is what I have decided on
  14. Moriske macrumors member

    Oct 19, 2015
    I understand that the price difference is small, unfortunately the performance difference too. Seems better to stabbing that money into additional memory, which you will need for your purposes ;)
  15. kohlson macrumors 68000

    Apr 23, 2010
  16. netnothing macrumors 68040


    Mar 13, 2007
    Yeah, I'm guessing performance won't be that much between the 395 and 395x. I'm just wondering if the Retina display and Adobe programs will be happier with the extra 2GB of video memory.

    BTW....lived in Marblehead for a few years!

  17. joema2 macrumors 68000


    Sep 3, 2013
    LR 6 definitely uses all available physical cores for import, preview generation and export. I posted the iStat Menus thread display here: http://forums.macrumors.com/threads/photo-editing-hardware-priority-5k-imac.1929824/#post-22109600

    However LR does not benefit significantly from hyperthreading during those tasks.
  18. eoren1 thread starter macrumors 6502

    Aug 17, 2007
    Thanks again everyone

    Just pulled the trigger - i7/512ssd/395

    Also got a great deal on a Samsung 850 EVO SSD 1TB to put in an external (drive was only $280!). Between that, the internal SSD, and my RAID5, should be good to go...

    Now to decide if I should get the Dell 27" monitor as a second screen or wait just a bit to profile this iMac first...

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