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Hellhammer

Moderator emeritus
Original poster
Dec 10, 2008
22,164
582
Finland
Background

TypeCPins.png


USB-C has four high-bandwidth lanes that can be dedicated to either USB 3.1 Gen 1 (i.e. USB 3.0 - 5Gbps) or DisplayPort 1.2. In addition to these four lanes, USB-C has separate USB 2.0 and power lanes that are available at all times. Running 4K at 60Hz requires the bandwidth of all four lanes, which would limit USB to 2.0, and for some reason Apple has disabled this, leaving users with no proper 4K support. The MacBook supports 4K at 30Hz just fine, but most users have found this to be unusable since even moving the cursor has a notable lag.

The Hack

While this topic surfaces quite frequently, very few seem to be aware of a hack that enables 4K at 60Hz. The hack is called mac-pixel-clock-patch-V2 and user reports here indicate it works flawlessly and is smoother than the SwitchResX 50Hz hack since the panel can run at its native 60Hz refresh rate. Basically, the hack forces all four high-speed lanes to be dedicated to DisplayPort 1.2, meaning no USB 3.0, but USB 2.0 and power is still delivered assuming that the device/cable/adapter supports these.

This Thread

The purpose of this thread is to act as a general wiki database for user experiences and displays, cables and adapters that work. This is a wiki post, meaning anyone can modify this with the idea of keeping this as up to date as possible, so people can quickly find information and buy supported equipment.

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Displays

Lenovo ThinkVision X1 - 27" 4K IPS $669

Reported to be working here. Has built-in USB-C port for video, data and charging, so no adapter needed. Built-in mic, camera and speakers work as well. However, the included USB-C cable does not work - see below for cables that have been confirmed to work.


Adapters

No specific adapters confirmed yet. This post mentions "a cheap USB-C to DisplayPort" working and technically all USB-C to DisplayPort adapters should work.


Cables

Apple USB-C Cable - NOT WORKING

Only for charging - cannot be used for video or data.

Monoprice USB 3.1 USB-C Cable 3ft - WORKING

Confirmed to be working here.

Belkin USB 3.1 USB-C Cable 3ft - NOT WORKING


Supports charging and perhaps data, but no video as reported here.

AUKEY USB 3.1 USB-C Cable 90cm - MIXED REPORTS


One user is reporting it works, whereas another one reports it not working.

Tenswall USB 3.1 USB-C Cable 3.3ft - NOT WORKING


Reported here.
 

w0rd3r

macrumors regular
Jun 4, 2014
145
51
France
Asus PB287Q - 28" 4K TN $429

I (w0rd3r) just tested it and it works at 1920 x 1080 HiDPI @ 60Hz, but no other scaled resolution like 1800p or 1440p. I used a Victsing adapter (http://www.amazon.com/dp/B0191PRS72/), so I'm not able to test a Clamshell mode, where I assume I'll be able to use every scaled resolution @ 60Hz.
 

Hellhammer

Moderator emeritus
Original poster
Dec 10, 2008
22,164
582
Finland
Asus PB287Q - 28" 4K TN $429

I (w0rd3r) just tested it and it works at 1920 x 1080 HiDPI @ 60Hz, but no other scaled resolution like 1800p or 1440p. I used a Victsing adapter (http://www.amazon.com/dp/B0191PRS72/), so I'm not able to test a Clamshell mode, where I assume I'll be able to use every scaled resolution @ 60Hz.

Does HiDPI mean that it's running at 4K, but with everything scaled to 1080p? What was the resolution before you applied the patch? Just trying to make sure you're running it at max resolution.
 

w0rd3r

macrumors regular
Jun 4, 2014
145
51
France
Does HiDPI mean that it's running at 4K, but with everything scaled to 1080p? What was the resolution before you applied the patch? Just trying to make sure you're running it at max resolution.

Indeed, that is what I meant. Looking through the Monitor menu, I can clearly see he receives 3840 x 2160 @60Hz. But the MacBook makes it look like 1080p HiDPI (so it is scaled down to 1080p, but looks really sharp thanks to the 4K display).

I forgot to add that I managed to run it 4K@60Hz only via mirroring.

Before applying the patch, I ran the display at 2160p @30Hz. I wish I could use different scaled resolutions though. Can you? If you need screenshots of a system report, here they are
 

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rtr1985

macrumors 6502a
Sep 17, 2012
507
186
Is this hack only enabled when connected to a 4K monitor and everything back to normal settings when disconnected?
 

rtr1985

macrumors 6502a
Sep 17, 2012
507
186
Cool. Seems crazy not a default option rather than system hack. I'm no computer expert, though.
 

tomislavf

macrumors regular
Nov 2, 2011
157
76
It's probably not a system option because Apple doesn't want to explain why USB is running at 2.0 speeds when a 4k @ 60Hz display is connected.
 

w0rd3r

macrumors regular
Jun 4, 2014
145
51
France
Regarding the clamshell mode, I'll be able to test it in the upcoming weeks since I'll receive the KADI Port (with 2 USB-C).
https://www.kickstarter.com/projects/thekadiport/the-kadi-port-a-macbook-essential
So I'll use one with the charger and the other one with the DisplayPort adapter I mentioned earlier.

I still don't know if I'll be able to use every scaled resolution just like an iMac or a MacBook Pro. If anyone can tell me which resolutions are available (as I said, for me it only works @1080p HiDPI @60Hz. Others are not available or @30Hz) it would be great!
 

Hellhammer

Moderator emeritus
Original poster
Dec 10, 2008
22,164
582
Finland
It's probably not a system option because Apple doesn't want to explain why USB is running at 2.0 speeds when a 4k @ 60Hz display is connected.

Some Intel slides also mentioned that 4K may require additional cooling on Core M chips, so Apple might have disabled it to avoid excessive throttling and other heat issues.

I did not

Give it a try. You should be able to run your 4K display at non-HiDPI resolutions as well, including 3840x2160 at 60Hz.
 
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w0rd3r

macrumors regular
Jun 4, 2014
145
51
France
Give it a try. You should be able to run your 4K display at non-HiDPI resolutions as well, including 3840x2160 at 60Hz.
I'll see if I can, but I've not found anyone able to tell me if it had every option or not.
1080p HiDPI is (unfortunately) useless for me, I'd like 1800p or 1686p.

Do you know if it works only in mirroring mode for others as well as for me ?
 

tomislavf

macrumors regular
Nov 2, 2011
157
76
I'll see if I can, but I've not found anyone able to tell me if it had every option or not.
1080p HiDPI is (unfortunately) useless for me, I'd like 1800p or 1686p.

Do you know if it works only in mirroring mode for others as well as for me ?

Well here's a screenshot where it's running without mirroring.

HCUB6QN.png


From https://v2ex.com/t/277410
[doublepost=1464800203][/doublepost]
Some Intel slides also mentioned that 4K may require additional cooling on Core M chips, so Apple might have disabled it to avoid excessive throttling and other heat issues.

For desktop use? Can't see it getting any hotter than playing a 3D game. Who knows... it's Apple :)
 

Agent OrangeZ

macrumors 68040
Mar 17, 2010
3,017
3,015
Planet Earth
Regarding the clamshell mode, I'll be able to test it in the upcoming weeks since I'll receive the KADI Port (with 2 USB-C).
https://www.kickstarter.com/projects/thekadiport/the-kadi-port-a-macbook-essential
So I'll use one with the charger and the other one with the DisplayPort adapter I mentioned earlier.

I still don't know if I'll be able to use every scaled resolution just like an iMac or a MacBook Pro. If anyone can tell me which resolutions are available (as I said, for me it only works @1080p HiDPI @60Hz. Others are not available or @30Hz) it would be great!

Thanks for the tag!
 

in Cider

macrumors member
Jan 28, 2016
59
15
Any other monitors working besides Lenovo?

I just patched my rMB running 10.11.5 and I'm up and running at a glorious 3440x1440 @ 60Hz on an LG 34UC98 connected through an Aukey USB-C hub with HDMI out.
 

ctyrider

macrumors 65816
Jul 15, 2012
1,034
611
I just patched my rMB running 10.11.5 and I'm up and running at a glorious 3440x1440 @ 60Hz on an LG 34UC98 connected through an Aukey USB-C hub with HDMI out.

34UC98 is not a 4K display though. I didn't think you needed a patch to run this display at 60Hz.
 

in Cider

macrumors member
Jan 28, 2016
59
15
34UC98 is not a 4K display though. I didn't think you needed a patch to run this display at 60Hz.

While its not 4k, the resolution is still too high for native 60Hz on my rMB. 50Hz is the max OS X will allow until after the patch.
[doublepost=1465144476][/doublepost]
its not a 4K display and you don't need a patch for it.

I did need to patch to get to 60Hz on my rMB, otherwise the max I could get to work was 50Hz.
 
Last edited:

BeatCrazy

macrumors 603
Jul 20, 2011
5,078
4,439
While its not 4k, the resolution is still too high for native 60Hz on my rMB. 50Hz is the max OS X will allow until after the patch.
[doublepost=1465144476][/doublepost]

I did need to patch to get to 60Hz on my rMB, otherwise the max I could get to work was 50Hz.

How usable is 4K at 50Hz?
 
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