How to get 4k @ 60Hz while charging?

Discussion in 'MacBook' started by matt2053, Jul 14, 2017.

  1. matt2053 macrumors 6502a

    Jul 8, 2012
    Simple question:

    With a 2017 12" rMB, how can I drive a 4K display @ 3840 x 2160 60Hz while charging the MacBook?

    My 4K display only has HDMI or DisplayPort ports (Dell P2715Q).

    When I am at my desk I want to have the MacBook in clamshell mode with external monitor, keyboard and mouse.

    If this is possible with my current monitor, I will get the 12" rMB. If it is not possible, I guess I will have to get the 13" MBP. My first choice is the 12" MB though.

    Thank you.
  2. Admiral macrumors regular


    Mar 14, 2015
  3. airattack111 macrumors member

    Dec 9, 2008
  4. Elwe, Jul 25, 2017
    Last edited: Jul 26, 2017

    Elwe macrumors regular

    Dec 30, 2006
    I have looked for a while, and have not seen any solution. Maybe it is a bandwidth problem; maybe we will not see a solution until Intel puts TB3 on the chip. It does not seem like Apple has any intention of putting a second port and/or another chip inside the existing chassis.

    I helped my friend recently make this very choice and in the end, she went with a dock running at 4K and 30Hz. Most of her work is static or "film". She really felt the size/weight difference of the two chassis, and happened to like having the extra color options.
    --- Post Merged, Jul 25, 2017 ---
    This dock is not capable of 4K at 60Hz, at least not without a special firmware that severely restricts bandwith to the other ports on the dock:

    --- Post Merged, Jul 25, 2017 ---
  5. matt2053 thread starter macrumors 6502a

    Jul 8, 2012
    Thank you for confirming what I suspected. I came to the same conclusion myself a few days ago and that basically rules out the 12" MacBook for me, which is disappointing.

    Fortunately I was in a position to be able to get the new 13" MacBook Pro instead. I was hoping for the ultra portability of the 12" MacBook, but the Pro is a good bit thinner and lighter than the 2015 model I had so it's fine.

    Thanks for your help!
  6. Graham Perks macrumors member

    Oct 2, 2003
    Austin, TX
    Unfortunate that the monitor cannot send power down the cable. Or are there monitors/connectors that will do this?
  7. Elwe macrumors regular

    Dec 30, 2006
    Yes, I think; but I am unsure exactly what you are asking. The OP was asking a question that happens to center more, it seems, around bandwith limitations or designs . . . somewhere, combined with the monitor mentioned. There are definitely monitors and/or adapters that will allow you to power a given monitor and Macbook via only one cable from the Macbook. Perhaps the best support is the on by LG sold by Apple:

    It is (now) more expensive than it was months ago as it used to be on sale by Apple. $700 is pretty expensive for this size of panel these days. And the port USB 2.0 speeds are real limitations for many, though mice and keyboards will be fine. This monitor was specifically designed for use with the Macbook, though it will also work fine with the Macbook Pro and other USB-C monitors with alt channel charging capability. It is the same panel used in the 21" iMac. The bandwith differences seem to come down to Apple including additional hardware (a TB3-capable chip) in the iMacs and Macbook Pros that they could not (or did not want to) fit into their 12" chassis.
  8. andy9l macrumors 68000

    Aug 31, 2009
    England, UK
    With a USB-C monitor, yes.

    I use a LG 27UD88 4K monitor and it works perfectly well @60Hz with my 2015 rMB, whilst also charging.
  9. matt2053 thread starter macrumors 6502a

    Jul 8, 2012
    If you have a USB-C monitor it's no problem. Those monitors can receive video and send power back to the Mac over the same USB-C cable. My problem was how to do this with a DisplayPort monitor. Because I need to do video to the monitor over DisplayPort, I need to use a dock or an adapter. However I could not find one that would both allow power to the MacBook and do video out over DisplayPort at 4K @ 60 Hz at the same time.

    I ended up getting a 13" MacBook Pro instead. Very happy with it, as even if there was a good dock solution with the 12", the combined cost would have been higher than just buying the Pro (I got the non-touchbar model).

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