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I am using Macbook Pro 13" 2015

To get 4k @ 60hz with HiDIP Make sure you get a Mini Display port to Display port cable like this one:

https://www.amazon.com/gp/product/B00C7RJQPY/ref=oh_aui_detailpage_o03_s00?ie=UT F8&psc=1

The U28D590 is set to DisplayPort 1.1 by default. Make sure you set it to DisplayPort 1.2.
Were you able to use this Samsung monitor in 4k @ 60hz and HiDIP? I have a mpb retina 15 early 2013 (GT 650M) and bought this samsung monitor (not yet arrived) but searching the Internet about this issue I'm almost canceling the purchase.
 
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Nope.
After too much digging, the best I can get is 2800x1575@60 (or 2880x1620@58) and this with a custom display override file I made (PM me if you need it).
HiDPI works (through SwitchResX), I have it at 2080x1170 and it looks quite good.
All in all, the result is much better than 1920x1080 or 2560x1440, but not 4K.
It's a shame, if I had bought the MBP a few months later, it would be true 4K and without any effort.
 
Nope.
After too much digging, the best I can get is 2800x1575@60 (or 2880x1620@58) and this with a custom display override file I made (PM me if you need it).
HiDPI works (through SwitchResX), I have it at 2080x1170 and it looks quite good.
All in all, the result is much better than 1920x1080 or 2560x1440, but not 4K.
It's a shame, if I had bought the MBP a few months later, it would be true 4K and without any effort.
Thanks for the quick response. I decided to cancel my purchase. My Macbook has some problems (some keys do not work due to water damage, the battery has more than 1,300 cycles and now the trackpad has stopped working) and since I can not buy a complete Top Case for it here in Brazil, I I decided to "turn it into a desktop", so I bought a Magic Trackpad 2, an external keyboard from Logitech and this 4K Monitor, but as the monitor will not work, I'd rather not even have anything, unfortunately. Difficult ... the repair in an authorized here is infeasible (absurdly expensive) and I can not get the part to repair.
 
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