Macbook Pro *Integrated Graphics* -> MDP-HDMI -> Samsung MU7000 4K TV: Stuck at 30Hz. But why?

Video Connector Adapters, Converters, and Cables DP-HDMI & MDP-HDMI
1

My goal: 3840x2160 @ 60Hz AND 2560x1440 scaled @ 60Hz on MBP Mid-2014 with Integrated Intel Graphics, Macos High Sierra → MDP-HDMI → Samsung MU7000 4K TV. The HiDPI scaled resolutions are important for my application. Please review my test results below before responding.

Test Config:
* “MBP with IG”: Mid-2014 Macbook Pro Retina with Integrated Intel Iris Pro graphics, High Sierra
* “MBP with DG”: Mid-2015 Macbook Pro Retina with Dual Intel Iris Pro + AMD Radeon R9 M370X Graphics, El Capitan
* Samsung UN49MU7000 49” 4K HDR TV, with HDMI UHD Color: ON
* Dell P2715Q 27" 4K Monitor
* Pluggable MDP-HDMI adapter bought Nov 5, 2018
* AmazonBasics High-Speed HDMI Cable, 10 Feet (https://www.amazon.com/gp/product/B014I8T0YQ)

Test Scenarios:

  1. MBP with DG → MDP-HDMI → HDMI cable → Samsung MU7000(HDMI UHD Color: ON): Success. 3840x2160 @ 60Hz AND 2560x1440 scaled @ 60Hz (as well as other scaled resolutions). No SwitchResX or other hacks required. Works right out of the box.

  2. MBP with IG → MDP-HDMI → HDMI cable → Samsung MU7000(HDMI UHD Color: ON): Failure. TV display is garbled, mostly all orange with horizontal strip of garbage on top. This is my “goal” hardware configuration described above.

  3. MBP with IG → MDP-HDMI → HDMI cable → Samsung MU7000(HDMI UHD Color: OFF): Stuck at 30 Hz. 3840x2160 @ 30Hz works, but there is no option for anything higher in Display Preferences. 2560x1440 @ 30Hz works, but is is obviously blurry and not scaled. No SwitchResX or other hacks required. 30 Hz is not useable for me.

  4. MBP with IG → Dell-supplied mDP to DP cable → Dell P2715Q: Success. 3840x2160 @ 60Hz AND 2560x1440 scaled @ 60Hz (as well as other scaled resolutions). No SwitchResX or other hacks required. Works right out of the box.

Analysis:

Scenario #1 proves that the MDP-HDMI adapter, HDMI cable, and Samsung TV all “work” and that the “MDP-HDMI → HDMI cable → Samsung MU7000” combination is in fact capable of displaying 4K and scaled 4K resolutions @ 60Hz - at least with the MBP with Dual Graphics as the source.

Scenario #4 proves that the MBP with IG “works” and that it is in fact capable of outputting 4K and scaled 4K resolutions @ 60Hz via displayport - at least with a 4K displayport monitor such as the Dell P2715Q.

Every individual component of scenario #2 has been proven to achieve the 4k@60Hz goal, yet this combination, fails. It would be easy to conclude that the Macbook Pro with Integrated Graphics doesn’t support 4k@60Hz output and scaled resolutions, except that #4 disproves this.

It should be noted that the MBP with DG is running El Capitan versus High Sierra for the MBP with IG. I would suspect this as a factor if it were not for the fact that this does not prevent #4 from working.

Other stuff I tried:

* Custom SwitchResX resolution with #2 above: This *did* produce 3840x2160@60Hz, but all attempts at a scaled 2560x1440 failed. 
* Enabling HiDPI mode and creating a custom plist file as described here: https://github.com/Floris497/mac-pixel-clock-patch-V2/issues/217. No change.

Questions:

* Why doesn't scenario #2 work? What am I missing here?
* Does the Pluggable MDP-HDMI adapter simply not support MBP with Integrated Graphics at 60Hz? If so, why not?
* Is there a firmware update that might help me out?

I would appreciate any help anyone can provide. Thanks.

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Hi,

Thank you for reaching out to us, I am sorry this is not working as expected.

Thank you for all of this testing and for the great write up!

Based on the monitors and televisions tested, this behavior is most likely being caused by the Intel Graphics Drivers default settings when connected to the Samsung monitor with HDR, and macOS not providing an option to disable HDR on the output.

HDR or High Dynamic Range increases the bits per color channel from 8 to 10, this requires DisplayPort 1.4 or HDMI 2.0b to function correctly. Most likely this system only support DisplayPort 1.2 and HDMI 1.4 ( per Apple’s product specifications ), likewise our graphics adapter supports up to DisplayPort 1.2 and HDMI 2.0 ( not 2.0b which is required for the additional necessary bandwidth ). Disabling HDMI deep color is equivalent to setting the HDMI port to HDMI 1.4 which supports up to 4K at 30Hz and 8-bits per color channel which is supported by the graphics adapter.

Intel’s graphics driver defaults to the highest color depth and will sacrifice the refresh rate to enable this. If the system does not reduce the refresh rate there will be more bandwidth than the miniDisplayPort to HDMI adapter is capable of handling and you will see display corruption.

The DisplayPort output worked at 4K 60Hz without error on the Dell display as this monitor does not support HDR and uses 8-bits per color channel, within the specifications of the miniDisplayPort on the system.

Unfortunately, macOS does not provide a method of setting the bits per pixel from 10 to 8 to override the Intel graphics driver. We do not have a fix for this situation, using the SwitchResX software has worked for some users in the past, however it has not been working as well with more recent HighSierra updates and we have had little feedback from systems running Mojave.

I am sorry we do not have a solution to get this television working with the 2014 MacBook Pro at 4K UHD 60Hz. I can offer to help return the miniDisplayPort to HDMI graphics adapter, if it is still within our return period and if you have no other use for it.

Please let me know how you would like to proceed, or if you wanted to try using SwitchResX to please let me know if this helps.

Pat.

3

Thanks for the quick reply, Pat.

I’m weighing my options. Most likely, I’ll sell the 2014 MBP IG and get another 2015 MBP DG so it will just work as expected, or just get another Dell monitor. I wonder how many people like me figured that the Dual Graphics option wasn’t important when they purchased, only to find out later that it’s really necessary for proper 60Hz operation with a 4k TV.

4

Hi,

Thanks for the update, I am sorry this did not work as expected. Using a computer monitor, such as the Dell, should get around this issue, a television without HDR should also work well.

Unfortunately this has started to become a more common issue as HDR televisions are becoming more common. Without the ability to adjust the color depth ( bits per color channel ) either in the operating system or on the televisions incompatibility will become more of an issue.

Future version of Thunderbolt 3 hardware will support DisplayPort 1.4 which is capable of HDR, and USB-C/Thunderbolt 3 to HDMI adapters will also be capable of HDMI 2.0b and 2.1 to support HDR. Unfortunately these are hardware changes that will only be available on newer systems and can not be back ported to older computers.

Please let me know if you have any additional questions, if not I will go ahead and close this topic after a couple of days.

Thank you,

Pat

5

Hello,

We’re closing this thread due to inactivity, but if you have any further questions please feel free to contact support@plugable.com and we’ll be happy to help.

Thanks,

Pat