Can you connect two LG UltraFine 5k Displays (albeit at lower resolution) to a Macbook Pro 2015 with two Thunderbolt 3 to Thunderbolt 2 adaptors?

LG UltraFine 5K Display

LG UltraFine 5K Display

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1 Answer from the Community

  • If you are using the MacBook Pro (Retina, 15-inch, Mid 2015) then it might be possible.

    There are four questions:

    1) Does the MacBook Pro (Retina, 15-inch, Mid 2015) support two 4K displays?
    The Apple web page "MacBook Pro (Retina, 15-inch, Mid 2015) - Technical Specifications" states that it supports up to two 4K displays. It doesn't specifically state 60 Hz though.

    2) Does the MacBook Pro (Retina, 15-inch, Mid 2015) support 4K at 60Hz?
    The Apple support page "Using 4K displays, 5K displays, and Ultra HD TVs with your Mac" states the MacBook Pro (Retina, 15-inch, Mid 2015) supports 4K@60Hz SST, but doesn't mention that two such displays are supported.

    To answer both of those, I have verified that two 4K@60Hz DisplayPort displays do work.

    Now for the LG 5K display:

    3) Does the MacBook Pro (Retina, 15-inch, Mid 2015) support 4K at 60Hz on the LG 5K display?
    The Apple support page "Use the LG UltraFine 5K Display with your Mac" states the MacBook Pro (Retina, 15-inch, Mid 2014) and later supports 4K@60Hz on the LG 5K

    4) Does the MacBook Pro (Retina, 15-inch, Mid 2015) support 4K at 60Hz on two LG 5K displays?
    The same Apple support page doesn't mention being able to do two displays at less than full resolution. The MacBook Pro (Retina, 15-inch, Mid 2015) only has one Thunderbolt 2 chip, and a Thunderbolt chip can support only two Display Port streams. The LG 5K uses two streams at 5K. If the LG 5K uses two streams at 4K, then you can only use one LG 5K display with the MacBook Pro (Retina, 15-inch, Mid 2015). However, it is possible the LG 5K uses only one stream at 4K (like the Dell 5K display). In that case, you could use two LG 5K displays at 4K on the MacBook Pro (Retina, 15-inch, Mid 2015). I think AMD graphics in macOS supports MST, so maybe two 4K displays will work even if each uses two streams.