I just bought a 4k monitor (AOC u2777pqu) for my MacBook Pro (Retina, 13 inch, Early 2015). The shop advised a mini-DisplayPort to HDMI cable, which gives me 4k resolution but when I tried it only provided a refresh rate of 30Hz.
The Apple support guide ( https://support.apple.com/en-sg/HT206587 ) suggests that the Thunderbolt cable will allow this model to run 4k at 60Hz.
My question whether getting a 'pure DisplayPort' ( mini-DisplayPort to DisplayPort cable – 4k certified) provide the 60Hz at 4k?
Best Answer
Officially, your model MacBook Pro will support up to 3840 by 2160 pixels at 30Hz or 4096 by 2160 pixels at 24Hz if using a HDMI connection, which explains your experience of 30Hz with your mini-DisplayPort to HDMI cable.
Your model MacBook Pro also supports up to 3840 by 2160 pixels at 60Hz using a Thunderbolt connection. Since your display supports both a 60Hz refresh rate and a DisplayPort connection, then using a mini-DisplayPort to DisplayPort cable of sufficient quality should achieve what you want.