How do external displays affect performance?

Discussion in 'MacBook Pro' started by adamjackson, Mar 11, 2015.

  1. adamjackson macrumors 68000

    Jul 9, 2008
    I've been thinking of getting an external display or 2 for my MacBook Pro Retina late,2013. It has the discrete GPU (2GB ram) & Core i7 w/ 16Gb of RAM.

    I'd like to get 2 displays, I'm thinking Dell 24" or 27" 4K displays running them at full resolution and still using the MacBook as a display that just has Outlook or Tweetdeck or something like that.

    It seems like you only need one DisplayPort to power one 4K monitor and I can use HDMI to power the other and keep that 2nd ThunderBolt Free for other tasks.

    My concern is will I see any flickering of windows, slowness? Time between switching full-screen apps, etc? Anyone running 4K setups and having issues?
  2. matty1551 macrumors 6502

    Jul 7, 2009
    You shouldn't see much of a performance hit. I recently spoke to an Apple retail manager regarding performance using external displays and he said he would consider a 1-2% drop in performance acceptable.
  3. adamjackson thread starter macrumors 68000

    Jul 9, 2008
    I've seen some mouse stuttering and drag / lag in activating Mission Control or switching full screen apps with the MBP + a single 24" 4K Dell monitor. It's fully supported by OS X using DisplayPort 1.2 (there's even a Kbase doc) but there is a noticeable lag that wasn't there before.

    Also with the MBP display closed and just using the 4K monitor, things do improve slightly. Could be related to me running the OS X beta program but so far, I'm not too happy. Will try running the dell at a lower resolution for a few days to see if it improves.
  4. Hieveryone macrumors 68040


    Apr 11, 2014
    It works FASTER for me. I have a 13" late 2013 and whenever I hook it up to my Dell 24" things are faster. I think that's because I'm not having to power the retina display.
  5. matty1551 macrumors 6502

    Jul 7, 2009
    My experience is that in Clamshell mode (external display with lid closed) performance is degraded significantly. The same handbrake encode took an extra 8 minutes in clamshell mode. The CPU goes from 2.5 average to 1.8 average during the encode.

    However, I believe that my board is somehow defective and Apple has offered to replace it if I'd like.

    Try monitoring your tasks with intel power gadget. It will tell you your cpu frequency, wattage, and temperature.
  6. campyguy macrumors 68040

    Mar 21, 2014
    There's a pretty long but useful thread about the two Dell 4k monitors - skip to the last 2-300 posts for the quality feedback as so many of the initial posts were about waiting for it or wading through the initial builds of the monitor. If you're thinking about one of the two Dell 4k monitors, don't wait too long....

    I have the same rMPB and the Dell P2715Q monitor, attached to the mDP port. I love it. I also have a second one attached to the rMBP via HDMI and a Mini Server via mDP, but that's a different story.

    I followed some of the advice in that long thread and changed the EDID of the monitor to get the Macs to recognize the monitor as an RGB monitor and spent $14 on SwitchResX. I wish this setup was available 25 years ago, and I'd still be using it today. The only add is that I've ordered two Herman Miller Flo arms (a Dual for my two monitors and a Plus with a laptop adaptor) to complete the package.

    As to the buy "now" bit - Adorama has the P2715Q on sale for $455 right now ( The lowest price I've seen on that monitor. I got a really good price on my monitors, but Adorama's price kills it and they add free expedited shipping (not the slow-boat-to-Hell shipping method that Dell uses).
  7. Putyouinmyoven macrumors newbie

    Feb 12, 2015
    I'm getting a new 2015 13" soon - I plan to use the HDMI out to hook it up to my (720p / 1080i) HDTV for watching movies / playing games, should I expect any performance dips / anything else I should know?

  8. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    I performed Macoh stress tests in clamshell mode and found no throttling (tested on a late-2013 13" i7/16/512).

    But then, my rMBP was propped up on the back end, plus I set the fans to idle at around 3000 rpm when in clamshell mode.

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7 March 11, 2015