iMac 5k 2015 - poor scrolling performance?

Discussion in 'iMac' started by tigersoul, Sep 20, 2016.

  1. tigersoul macrumors newbie

    Sep 20, 2011
    I knew retina has it's toll on the gfxcard and that iMacs don't exactly have powers to spare in that department, but I definitely hoped for a better experience than this. I just got my maxed out iMac 27 inch late 2015. The only thing not being maxed out is the gfx card as I felt it wasn't worth the huge step in $$$ to go from 395 to 395x. I still have the next to the best gfx available after all in this machine.

    Although the screen is gorgeous and even more gorgeous when put into scaling mode, I noticed very early on during my tests that there are repercussions to retina. Just downloading Evernote and opening the todo-list for my iMac-tests revealed issues. Scrolling the note of about 2-3 pages was somewhat laggy and slower to respond than my old machine without retina. On to just scrolling through a pdf quickly and again: it is oh so clearly worse in performance. So bad actually, that it looses that magical "mac feeling". Scrolling in Chrome and Safari was fine so I was lead to believe that good scrolling needed programs with gfx acceleration in use. Just a speculation, might be something else.

    Is this something that you notice? I've googled a bit but haven't found a huge number of threads. They are mostly about the macbook pro's and rarely about the iMacs. Maybe my demand of having at least equal performance is high when taking retina into the picture and maybe I'm letting things bug me that others won't take note of but really, as it feels now, this computer is going back to Apple to await the 2016 model.
  2. Mikey86uk macrumors 6502

    Jul 3, 2010
    Scrolling on everything I've used on my maxed out 2015 iMac is smooth.

    Only difference is I have the 395X
  3. Krevnik macrumors 68040


    Sep 8, 2003
    When scrolling, an app is still required to help "fill in" any missing parts of the view being scrolled. If your code isn't fast enough for any reason to draw in these parts, then it will lag. Apps like Safari have had a lot of work done for the sake of scrolling performance, including caching the output of webpage rendering. Evernote likely draws in a "just in time" manner, right as the OS calls on it during the scroll itself. Doing this is more expensive on a Retina display because you are drawing 4x the number of pixels as you scroll, which requires more resources.

    So some of this is coming from the higher pixel count, and some of it is coming from the app. Every app will be somewhat different here, and how vigilant they have been checking machines like the 5K for performance problems. That said, getting good scrolling performance on a 5K display isn't exactly easy work, since it isn't just about graphics acceleration, but also how quickly the application can figure out what should be displayed during scroll as well, and to draw it into a texture for the GPU to draw.
  4. maflynn Moderator


    Staff Member

    May 3, 2009
    No scrolling issues for me - I'm on a M395 and its buttery smooth
  5. IngerMan macrumors 6502a


    Feb 21, 2011
    Same here same machine as Mike, smooth as molasses
  6. tigersoul, Sep 21, 2016
    Last edited: Sep 21, 2016

    tigersoul thread starter macrumors newbie

    Sep 20, 2011
    I made a video to illustrate the poor performance while scrolling through a PDF in Preview. See the specs of the compared computer, monitor and gfx-card in the video. The gfx in the compared computer indeed is about 25% stronger or so, but it shouldn't make THIS much of a difference really. Especially since the compared computer is running a 4k screen at native resolution AND a 19" monitor, while the iMac is only running it's own screen.

    As you can see, when scrolling quickly through the PDF at the iMac 5k 2015, I'm ending up with white pages as the computer cannot keep up. At the compared computer, I have no issue. The difference is quite striking so I'm somewhat puzzled when you say that you haven't noticed anything but buttery smooth scrolling. Apart from the showcased Preview, I'm also having questionable scrolling in Evernote. It's not bad to the same degree but it's still noticeably worse.

    May it be the m395x making all the difference here? Feels kind of ****** that I'd have to shell out that kind of amount to get decent scrolling.

    Link to youtube-video:
    Link to the PDF used for testing:

    I'd love to hear about your experiences on fast-scrolling the PDF above. You never know, I may be doing things here that isn't "normal".

    Absolutely. I do realize that retina must take a toll somewhere and I had quite some worry about the relatively poor performing iMac graphics in regard to this. The strange thing is my comparsion. The other system does have a 4K screen and while it's running natively, it should still be closer in performance to the iMac. I know that I can be somewhat of a critical user but I've always been EXTREMELY happy with macs and I do most certainly not associate these computers with performance issues. If that's the new world order due to retina, I'm not such a happy camper anymore.

    EDIT: Now tried the same PDF in Preview on my Macbook Air. It's not retina but it's also not powerful at all. The PDF scrolls perfectly fine there. Once again: not retina, but it's an unacceptable compromise when we're talking about a computer costing 4.5 times that Air.
  7. =E= macrumors regular


    Nov 8, 2013
    Same with mine. I have the same iMac and it is really smooth.
  8. jerwin macrumors 68000

    Jun 13, 2015
    Imac 5k with m290x. No lag whatsoever.

    On the other hand, my iMac has trouble smoothly rendering the pdf linked here.

    Tychonis Brahe Astronomiæ instauratæ mechanica

    Simply disgraceful.
  9. tigersoul thread starter macrumors newbie

    Sep 20, 2011
    Being frustrated and looking through things I quickly bootcamped into Windows 10. Guess what? NO SCROLLING LAG what so ever! Not even for that huge PDF. Sure makes me a bit angry.

    I'm surprised to hear that nobody else has seen the issue. Maybe I have a hardware issue or something? Something tells me that isn't it however.
  10. danielwsmithee macrumors 65816

    Mar 12, 2005
    When I run into stuff like this I generally try to recreate the problem on a new account, and if it still happens on a clean install.

    Have you tried creating a brand new account, logging out and logging into the pristine account?

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