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I own a MacBook Pro 15" 2015 with a Thunderbolt 2 port. I have recently bought a Samsung cj791 Thunderbolt 3 monitor (3440 x 1440 @ 100Hz; 85W Power Delivery)

I plan on connecting the monitor to my Mac using: a) A Thunderbolt 3 male to Thunderbolt 2 female adapter and b) a regular Thunderbolt 2 cable

These are my questions:

  1. Will this work at all (I have read it didn't before High Sierra)?
  2. Will I be able to go up to the full 100Hz this way at the full resolution? (Another post said TB 2 works with 4K @ 60HZ which is the same data rate - a little more even)
  3. I have read connecting 2.0 USB peripherals through the monitor is possible, does TB 2 also support USB 3.0 throughput?

Thanks.

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  • If you want to link to exact posts saying 4k works or doesn’t work, I can edit my answer. Have you looked up the Mac resolution and refresh your specific Mac offers?
    – bmike
    Nov 23 '20 at 21:23
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Yes in general. I use the same adapter to run all manner of USB-C and Thunderbolt 3 displays from 2013 Mac Pro and MacBook Air and Pro from the same era. You don’t get any extra resolution than the Mac could drive originally using adapters that shipped when the Mac in question was brand new.

I’m delighted with 5k displays running over the Thunderbolt 2 and all USB and Thunderbolt hubs I have tested work at full Thunderbolt 2 speed. Since USB-C and 3.0 is less speed than Thunderbolt - they all work fine in my experience.

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  • Thanks for the answer. Do you think I can get over 60hz so 100hz though? And also, do the hubs work with USB 3.0?
    – Fyn
    Nov 23 '20 at 21:38
  • @Fyn yes - I hopefully clarified the USB 3.0. You have to check if your mac can do 100Hz - this setup won’t magically make it faster. If it works to run any display at 100 Hz - it will work through this setup. If it can’t drive it, then no. The limitation isn’t the cable or the adapter - it’s in the math. Pixel count * bit depth * refresh rate will saturate the GPU - not the cables.
    – bmike
    Nov 23 '20 at 21:40
  • Alright, perfect that basically answers everything. I made sure to go for the 2 GPU one with an extra AMD card so my hopes are high but I won't be terribly disappointed if it's only 60hz because I bought the monitor with upgrading my Macbook in the next few years to make use of the TB3 PD feature anyways.
    – Fyn
    Nov 23 '20 at 21:47
  • And the new M1 Air can run the 5K display over USB-4 / Thunderbolt so you are well situated for much faster graphics soon. @Fyn Welcome to the site - next time, try to stick to one question per question. It works MUCH better for everyone
    – bmike
    Nov 23 '20 at 21:51
  • Alright, got it. Yeah, I am really looking forward to what Apple does with the 16" refresh, not because I will buy it, but because it will probably shake up the whole market for the benefit of all consumers even non-Apple.
    – Fyn
    Nov 23 '20 at 22:00

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