4k60 over DP 1.2 on late 2013 iMac

[amomchilov]

Hey guys, does anyone have experience with using 4k displays on the Late 2017 iMac? I was only able to get 30 Hz, despite the site claiming that 4k60 is supported.

I am not using HDMI, but rather a mDP to DP cable, which I know works, because my 2015 MBP drives these displays at 4k60 using it.

I have tried using SwitchResX, with and without the IOKit patch, to key in a custom resolution (4k@60), but frankly, I don't know if I'm using the correct settings. I copied the front/back porch, sync width, etc. from the info I found in the exported EDID.

See my question on Ask Different for more detail: https://apple.stackexchange.com/questions/310563/difficulties-with-4k60-support-on-my-late-2013-27-imac

Related issue: https://github.com/Floris497/mac-pixel-clock-patch-V2/issues/20

[Floris497]

You only have to choose resolution and refresh rate, the other settings should be equal.. maybe chech the other port if you have more? Could be that one port can only do 30Hz..

[amomchilov]

@Floris497 Hey, thanks for responding. I have tried both ports (on their own, not just simultaneously), with two different monitors models (HP Envy 27S and Asus MG28U).

The HP Envy 27s only shows up as supporting 2560x1600@60Hz, but I was able to get 4k60 out of it with SwitchResX.

The Asus MG28U shows up as supporting 4k, but only at 30Hz.

In neither case was I able to get 4k60, despite the same cable/monitor combo working with my 2015 MBP at 4k60

[Floris497]

Hm.. i have no idea then.. it should just work without the patch. did you try playing with DP1.2/1.1 and MST/SST settings in the monitor?

[amomchilov]

Neither does Apple, apparently. I have my monitors set to DP 1.2, but 1.1 didn't work, either. Neither monitor has MST/SST settings. I wasn't able to find out concretely whether they are MST or SST (is there somewhere I can check in macOS?)

[Floris497]

I didn't really find a way to check in macOS if it's SST or MST didn't really look for it either.. if any patch would work it would be CoreDisplay

[amomchilov]

@Floris497 Oops I mixed them up in my original post. I wrote IOKit, but I meant CoreDisplay.

[Floris497]

What does CoreDisplay-patch.command status Report?

[amomchilov]

Currently:

SIP looks to be disabled, all good!

(otool) Detected unpatched CoreDisplay on OS X 10.13.2 17C88.

but previously it was patched (still didn't work). Should I repatch to quote you exactly what it says while patched?

[Floris497]

Ah, i was just wondering if the patch was successful.. it probably wasn't because of latest updates.. could you try to patch it again?

[amomchilov]

@Floris497 It was successful, and I had tried it both on the build 17C88 and 17C205. It currently incorrectly reports 17C205 as 17C88

Just patched again:

$ ~/mac-pixel-clock-patch-V2/CoreDisplay-patcher.command
SIP looks to be disabled, all good!

(otool) Detected unpatched CoreDisplay on OS X 10.13.2 17C88.
SIP looks to be disabled, all good!
Patching CoreDisplay with patch version 4
Password:
Re-signing /System/Library/Frameworks/CoreDisplay.framework/Versions/A/CoreDisplay
/System/Library/Frameworks/CoreDisplay.framework/Versions/A/CoreDisplay: replacing existing signature
Running 'sudo update_dyld_shared_cache' (Might need re-run after reboot) - CAN TAKE A WHILE (Maybe even 10/30 minutes)update_dyld_shared_cache: warning @rpath install name for system framework: /System/Library/PrivateFrameworks/AssetCacheServicesExtensions.framework/Versions/A/XPCServices/AssetCacheTetheratorService.xpc/Contents/Frameworks/MobileDeviceKitLite.framework/Versions/A/MobileDeviceKitLite
update_dyld_shared_cache: warning @rpath install name for system framework: /System/Library/PrivateFrameworks/BiometricKitUI.framework/Versions/A/BiometricKitUI
update_dyld_shared_cache: warning @rpath install name for system framework: /System/Library/PrivateFrameworks/BroadcomWLAN.framework/Versions/A/BroadcomWLAN
update_dyld_shared_cache: warning @rpath install name for system framework: /System/Library/PrivateFrameworks/WirelessDiagnosticsSupport.framework/Versions/A/WirelessDiagnosticsSupport
update_dyld_shared_cache: warning @rpath install name for system framework: /System/Library/PrivateFrameworks/BookKit.framework/Versions/A/Frameworks/BookKitFoundation.framework/Versions/A/BookKitFoundation
update_dyld_shared_cache: warning @rpath install name for system framework: /System/Library/PrivateFrameworks/SetupAssistantSupport.framework/Versions/A/SetupAssistantSupport
update_dyld_shared_cache: warning @rpath install name for system framework: /System/Library/PrivateFrameworks/Swift/libswiftDemangle.dylib
update_dyld_shared_cache: warning @rpath install name for system framework: /System/Library/PrivateFrameworks/Swift/libswiftRemoteMirror.dylib
update_dyld_shared_cache: i386 incorporating 627 OS dylibs, tracking 1047 others, building closures for 254 executables
update_dyld_shared_cache: x86_64h incorporating 1259 OS dylibs, tracking 1773 others, building closures for 2107 executables
update_dyld_shared_cache: warning: i386 adding dependents to /System/Library/PrivateFrameworks/Assistant.framework/Versions/A/Resources/Assistant Plugin.ibplugin/Contents/MacOS/Assistant Plugin: required dylib '@rpath/InterfaceBuilderKit.framework/Versions/A/InterfaceBuilderKit' not found, needed by '/System/Library/PrivateFrameworks/Assistant.framework/Versions/A/Resources/Assistant Plugin.ibplugin/Contents/MacOS/Assistant Plugin'
update_dyld_shared_cache: warning: x86_64h adding dependents to /System/Library/BridgeSupport/ruby-2.3/bridgesupportparser.bundle: required dylib '@rpath/libclang.dylib' not found, needed by '/System/Library/BridgeSupport/ruby-2.3/bridgesupportparser.bundle'
update_dyld_shared_cache: warning: x86_64h adding dependents to /System/Library/PrivateFrameworks/Assistant.framework/Versions/A/Resources/Assistant Plugin.ibplugin/Contents/MacOS/Assistant Plugin: required dylib '@rpath/InterfaceBuilderKit.framework/Versions/A/InterfaceBuilderKit' not found, needed by '/System/Library/PrivateFrameworks/Assistant.framework/Versions/A/Resources/Assistant Plugin.ibplugin/Contents/MacOS/Assistant Plugin'
update_dyld_shared_cache: warning: x86_64h adding dependents to /System/Library/QuickLook/Audio.qlgenerator/Contents/MacOS/Audio: required dylib '/Library/Frameworks/iTunesLibrary.framework/Versions/A/iTunesLibrary' not found, needed by '/System/Library/QuickLook/Audio.qlgenerator/Contents/MacOS/Audio'
Closing..

[Floris497]

That's because the file is exactly the same.. so it'll see it as an older version. And that's actually nice to know. So even with Switchresx it doesn't work now?

[amomchilov]

@Floris497 Not activated - invalid?

Here's is the config and the exported EDID: