Can I do 4K@60hz with my early 2015 MacBook Pro Retina?
I have a MacBook Pro Retina early 2015 8 GB and Intel 6100 1536Mb.
Today I used an HDMI cable to my TCL 55" TV (TCL U55S6906 / Chassis NT667E-EU) and when running Mac OS X the text is blurry and only at 30Hz. While running Windows 10 it looks better but is still at 30 Hz.
Also, sometimes it goes black for a second or two, and sometimes it shows green lines and plays a strange sound.
My TV only has HDMI but I wonder if I could get 60 Hz with a Thunderbolt 2 cable to HDMI 2.0? Does anyone know why it shows those lines and makes those sounds (which remind me of interference).
Solution 1:
I have a similar device (Early 2015 rMBP with 16 GB running macOS Sierra 10.12.6) and can confirm that it will power an external 4K display at 60 Hz - it's supposed to power two external displays at 4K (3840x2160) in addition to the builtin display, in fact. However, there are anomalies on my side when it comes to the refresh rate depending on my screen setup. Also, MacOS does not let me choose the refresh rate for the 4K screen when it's connected through the Mini DisplayPort to DisplayPort cable - other than feeling the difference, I only see the refresh rate in the system profiler.
Hardware: rMBP Early 2015 with macOS 10.12.6 and 16 GB RAM; Display 1 (old): 900x1440 via mDP-DVI adaptor and DVI cable; Display 2 (4K): 3840x2160 via mDP-DP cable
Scenario 1 = 1 desktop: rMBP is closed, Display 1 (old) is disconnected, Display 2 (4K) is the only desktop displayed at 3840x2160 @ 60 Hz
Scenario 2 = 2 desktops with builtin screen: rMBP is open at 2560 x 1600 Retina, Display 1 (old) is disconnected, Display 2 (4K) is connected with 3840x2160 @ only 30 Hz
Scenario 3 = 2 desktops without builtin screen: rMBP is closed, Display 1 (old) is connected with 900x1440 @ 60 Hz, Display 2 (4K) is connected with 3840x2160 @ only 30 Hz
Scenario 4 = 3 desktops: rMBP is open at 2560 x 1600 Retina, Display 1 (old) is connected with 900x1440 @ 60 Hz, Display 2 (4K) is connected with 3840x2160 @ 60 Hz
To sum up, this means that my early 2015 rMBP 13" will only display 4K @ 60 Hz on the screen capable of doing so if either all 3 displays are active or the 4K display is the only active display. The refresh rate on the 4K screen is dropped to 30 Hz if it's one of only two active displays. This result has persisted despite restarting my Mac but I do not know if this behavior is limited to my example. If any reader has a logical explanation and/or solution for this, please post your answer.
Solution 2:
Can I do 4K@60hz with my early 2015 MacBook Pro Retina?
It's possible but not exactly fun. I'm using a Sony 43" 4k TV with HDMI 2.0 right now.
For some reason the MBP insists it can only run it at 30Hz, but with a piece of software such as SwitchResX you can manually add your resolution/refresh rate combination to the list of "supported" resolutions. You'll have to disable System Integrity Protection (which normally prevents system files from being modified - mostly for security purposes) to add custom "supported" resolutions to the Mac, which involves a reboot once to turn SIP off and again to turn it back on, all the while being more vulnerable than normal to viruses, although probably not vulnerable enough to worry too much as long as you remember to turn it back on.
You'll also need an active (Mini-)DisplayPort to HDMI 2.0 adapter. The HDMI ports on the MBP are 1.4 and not fast enough, but the Mini-DisplayPort ports are fast enough. The active part is needed because otherwise it will pipe the same 1.4 as the HDMI ports if you use a "dumb" cable/adapter.
While running Windows 10 it looks better but is still at 30 Hz.
You may have a BGR panel. Most monitors have a pixel order of (from left to right) red, then green, then blue, but some do it backwards and OS X doesn't seem to be able to handle it sometimes.
Also, sometimes it goes black for a second or two, and sometimes it shows green lines and plays a strange sound.
This happens to me too. I think my cable is going out but I haven't bothered to replace it, but you could try that.