4K = bad performance. what should I upgrade?

Discussion in 'Mac Pro' started by damian0815, Oct 22, 2014.

  1. damian0815, Oct 22, 2014
    Last edited: Oct 24, 2014

    damian0815 macrumors newbie

    Oct 22, 2014
    I recently upgraded my GPU to an Nvidia GTX660 (edit: was 640) to support 4k@60Hz, and it looks and feels absolutely amazing - but I'm taking a severe performance hit on text rendering, which is a problem when running Xcode full screen at 4k, which is what I do most of my day.

    My CPU is a Core i7-870 running at 2.93GHz, which although it's nearly 5 years old, is still a solid CPU as far as I understand it. I'm running off an SSD, I have maxed out the RAM with the fastest DIMMs that the system will support (1600MHz), but it's still not fast enough.

    So I'm looking at buying a new system, but on clock speed alone, the new iMac Core i5 with Retina display doesn't actually look that much faster than what I have (3.5GHz vs 2.93Ghz).

    Has anyone gone a similar route? I mean, 2010-era Mac upgrade to 2014 era with similar clock speed - do you really notice a performance boost, even if the clock speed of the CPUs stays roughly the same?

    Edit: Derp! I had the card in a PCIex4 slot. Put in a PCIex16 slot, everything is fine.
  2. Asgorath macrumors 68000

    Mar 30, 2012
    CPU clock speed alone is a terrible performance indicator. Each CPU generation gets faster at similar clock speeds, you'll notice that the speed itself hasn't really gone up all that much but there's probably at least a 2x overall performance increase in the last 5 years. I believe AnandTech or some other website did a comprehensive study of CPU performance, you might want to go take a look at that. Right now, I'm running a Core i7 4770K at 3.5GHz, and noticed a massive improvement over my old 2010 Mac Pro with a 3.2GHz Nehalem processor.

    Having said all of that, your GPU will be the limiting factor at 4K resolution, especially if you're only using a GTX 640 (the low-end GK107). You have the luxury of being able to drop in a PCIe graphics card, and should look at investing in a modern mid-range to high-end GPU to drive such a large display.
  3. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    You cannot compare the processors from different architectures using clock speed. It won't tell you anything.

    I hate myself for doing this, but Geekbench is the easiest to way to show you the difference

    GB3 (32bit free test): (single core - multi core)

    i7 870 ~2200 - ~8000

    i5 4690k ~4100 ~11500

    The i5 iMac will smoke your CPU and if your Xcode projects are complex, it will speed up compilation times a lot.
  4. damian0815 thread starter macrumors newbie

    Oct 22, 2014
    Oh, that's great to hear - thanks!

    Actually I mis-typed - it's a GTX660 that I have, and I just bought and am just out of the 2-week right-of-return period. TBH I struggled to find a video card that would support 4K@60Hz on OSX - couldn't find any information about if any of the 700-series were supported.

    Anyway, When I profile Xcode itself using Instruments, the performance hit is dominated by the time to assemble and draw the NSTextView driving the code editing window. For comparison I can make Firefox or Chrome full-screen and I don't have any of the same problems I do when editing code, which leads me to believe I'm CPU bound...
  5. Asgorath macrumors 68000

    Mar 30, 2012

    I have a hard time believing you're CPU bound at 4K, but YMMV.
  6. damian0815 thread starter macrumors newbie

    Oct 22, 2014
  7. goMac macrumors 604

    Apr 15, 2004
    The 660 is probably not a great performer for 4k.
  8. handheldgames, Oct 23, 2014
    Last edited: Oct 23, 2014

    handheldgames macrumors 68000


    Apr 4, 2009
    Pacific NW, USA

    The 990x these days is going for 400ish and delivers:

    Geekbench3 (64-Bit test): (single core - multi core)
    2905 - ~16640

    Just how many Pro apps use a single core these days?

    On the cMP, one can upgrade to a PCIe x4 ssd. Apple's latest chips are the fastest on the market, at 1.4GB/s. Slower versions pulling 1.1GBs and can go for $600ish. Internal PCIe SSD's on the riMac are limited to an x2 interface and 800MB/s. Unless you pay for the high-priced Thunderbolt options...

    The $300 970GTX already squishes the 290X. The $450 980X takes the crown. The 290x can also be picked up for $300ish.

    A fast video card and PCIe ssd will take most workflows to the stratosphere for a much cheaper investment.

  9. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    Agreed. This would be a better path to follow
  10. ThoreEliasson macrumors newbie

    Oct 21, 2014

    are all Maxwell equipped nVidia cards without any further tweaking 4K enabled in 10.10.?
    I am looking into a GTX 970 myself and would love to know.
    Thank you so much!
  11. damian0815 thread starter macrumors newbie

    Oct 22, 2014
    More confusion!

    I just tried out my friend's Macbook Pro 2014 with discrete GPU (GTX 750M). After we completely disabled the internal Iris Pro, he was able to drive both his internal 3880x2160 (Retina) screen and my 3840x2160 simultaneously from the GTX 750M, running Xcode fullscreen without any lag at all.

    Since the GTX660 is supposed to be more performant than the GTX750M (http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107-7.html), this would point to some other problem with my system compared to his. The two obvious ones are the PCIe connector (mine is PCIe x4, his is PCIe x8) and the CPU (mine is Nehalem, his is Haswell).


    It would seem so. Check the TonyMacx86 forums, the Hackintosh folks are some of the best ways to find out about GPU compatibility on Mac Pros -- what works on a Hackintosh ought to work on a Mac Pro, running the same OS version at least.
  12. damian0815, Oct 24, 2014
    Last edited: Oct 27, 2014

    damian0815 thread starter macrumors newbie

    Oct 22, 2014
    Ok, so if you put a PCIex16 GPU in a PCIex4 slot you get ... a quarter of the performance.


    Turns out a GTX660 is plenty usable, if it's in the right PCIe slot.
  13. damian0815 thread starter macrumors newbie

    Oct 22, 2014
    Final word on this: My friend let me try my GTX660 in his Core i5-4670 based Hackintosh, with my 4K monitor.

    Smooth as butter.

    So I'm definitely CPU bound.
  14. ha1o2surfer macrumors 6502

    Sep 24, 2013
    It's probably more of a driver issue. a GTX 660 is no slouch and can't be compared to a 750M. The 660 is more powerful by a factor of 3.

    An 870 and a 4670 is around 35% of each other in performance. I doubt that is causing an issue.

    Having a 660 in a x4 slot won't affect 4k performance unless you're playing a game. No discussion there as I run a 780ti at 1080p over thunderbolt 1 at 80-90% of the performance.

    Who knows what else it can be lol maybe that x4 slot was only running x1 mode? lol
  15. lowendlinux Contributor


    Sep 24, 2014
    North Country (way upstate NY)

    You upgraded graphics and the graphics is smoother the processor has nothing to do with it in this instance.
  16. damian0815 thread starter macrumors newbie

    Oct 22, 2014

    GTX660 on my i7 870 (in the PCIe-x16 slot) = acceptable (but not great) performance
    GTX660 on my friend's i5 4670 = amazing performance

    changing variable = CPU :. (probably) CPU caused the difference.
  17. goMac macrumors 604

    Apr 15, 2004
    FWIW, Xcode's on screen layout happens on the CPU, not the GPU.

    In OS X only entire windows hit the GPU. For the most part, the actual drawing of everything within a window is done on CPU. There are a few exceptions for apps that use things like OpenGL, but Xcode does not.
  18. damian0815 thread starter macrumors newbie

    Oct 22, 2014
    Oh, that's very useful to know.

    So, right - if I'm getting drawing bottlenecks it's most likely CPU related. That pretty much confirms what the evidence says.

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