4K Display and Retina MacBook Pro 13"

nobody has because apple does not support it

Hi,
With the 2013 13-inch Haswell rMBP it is possible to run at 3840x2160 or 1080P HiDPI over DisplayPort at 52Hz. This is because the max clock rate for the 13-inch over thunderbolt 2 is 450 MHz.

To get this resolution, use the settings in the screenshot I've made with switchresx (attached).

If you want 60Hz or even higher HiDPI settings, you can do this via picture by picture mode with a DP and a HDMI connector. There's an extensive thread on this in this forum.



Edit.. And yes, I did this with the same monitor you're using!

Sure, once you get 3840x2160 working in switchresx if you go to "current resolutions" there should be an option for 1920x1080 HiDPI, just select it and you should be good to go, as simple as that!

If you want to try and get 60Hz instead of 52Hz and some other HiDPI options working check out this thread:

https://forums.macrumors.com/threads/1735590/

@w0rd3r

Yep, if you're running a 4K display off of a late 2013 13-inch rMBP you should definitely be able to get 52 Hz (technically it's like 51.7 Hz) with the configuration I attached! HiDPI at 1080P should just work when you put in this setting as long as you have HiDPI options enabled. The only thing I don't know is whether or not apple would have disabled this in Yosemite, but I highly doubt it.

Besides the 52 Hz vs. 60 Hz thing, the only other issue to think about is that Apple doesn't seem to be allowing HiDPI options above 1080P on the 13-inch. For example, on the 15-inch you can get a HiDPI that "looks like" 1440P or even 3200P which gives you a bit more real-estate. You can get these resolutions working if you drive two panels (see the same thread).

That being said, the portability of the 13-inch is worth it in my opinion over the extra 8Hz at 4K. 52Hz seems totally fine! While 60Hz feels buttery smooth for day to day operation, 52Hz is almost there... I don't really notice the difference unless I'm looking for it. And yes, it's WAY better than 30Hz, which feels unbearable.

Just some technical info on the 52Hz thing, I think it stems from a hardware limitation from this chipset... according to intel this is what's going on:


DisplayPort 1.2 / eDP:
H-Processors: 3840 x 2160 @ 60 Hz
U-Processors: 3200 x 2000 @ 60 Hz
Y-Processors: 2560 x 1600 @ 60 Hz


The H-processors are used in the 15-inch, and the U-processors are used in the 13-inch rMBP. Since 3200x2000 is possible at 60Hz using the max bandwidth of the chipset... you could extrapolate that going to 3840x2160 should be possible at refresh rates higher than 30Hz... it must be about 52Hz!

jonisign said:

...

Click to expand...

Hmm - if we figure 3200*2000*24bpc*60hz = 9.216 Gbps (10 Gbps with overhead?), changing the variables I get ~46.30hz for 3840x2160. Where am I losing you?

Yeah I suppose you're right... One thing to keep in mind is that the 2013 models have thunderbolt 2 which allows for 20 Gbps... all I know is that 51.7Hz is what I'm able to get from a 450Mhz clock that this model provides over TB2, whereas you get 300MHz over HDMI (and I'm assuming the 2012 rMBP models)

jonisign said:

Yeah I suppose you're right... One thing to keep in mind is that the 2013 models have thunderbolt 2 which allows for 20 Gbps... all I know is that 51.7Hz is what I'm able to get from a 450Mhz clock that this model provides over TB2, whereas you get 300MHz over HDMI (and I'm assuming the 2012 rMBP models)

Click to expand...

If you have it running then you've got better info than me I'm just trying to calculate this stuff before I make a purchase. Its a pity that its so close but not quite there.

Yeah, understandable!

One thing to note is that Intel may have just reported 3200 x 2000 @ 60 Hz because it is some resolution that makes sense... not the possible max you could possibly get 60 Hz at... my bet would be that there is some resolution between 3200 x 2000 and 3840 x 2160 that would let you achieve 60 Hz over a single stream with these U-series processors.

That being said, I think the most important factor is the 450 MHz pixel clock speed on the 13-inch rMBP. With the settings that I posted in switchresx you can see that given a 450 MHz clock you can get to 51.702 Hz scan rate. My monitor is accurately reporting a signal of 3840x2160 at 52 Hz, no doubt about it.

Yup, it's just that command to enable it! You may need to reboot? Not sure.

Right, so, there aren't any 3200 x 2000 screens on the market, either, right? Maybe some weird laptop resolution? My guess is that they just picked some resolution that worked with 60 Hz to report that they tested with some panel, maybe a laptop. Maybe they didn't have anything between 3200 x 2000 and 3840x2160, so they reported 3840x2160 at 30 Hz rather than some strange (but nicer!) refresh rate like 51.7 Hz...

And yes, between HiDPI and without there is a huge difference, I agree! HiDPI is much cleaner.

Between 52 Hz and 60 Hz there is a difference, but is very subtle, I barely notice it. What you could do is try to simulate the 52 Hz experience for yourself on your current monitor. If you go to switchresx you can create a custom resolution at 52 Hz for the resolution you want, restart your computer, and see how it feels!

Also, keep in mind that I achieved this result with a Samsung UD590 monitor... not sure what you were planning on using! No idea how this would work on one of the other (very expensive) 60 Hz 4K monitors on the market... to my knowledge the only 4K monitor that can do 60 Hz over single stream is the Samsung... I think the super expensive sharp is doing it over multi-stream, which is less ideal, and I think it might not even be properly enabled for the 13-inch in OS X. However, windows handles all of this over MST very nicely, and you can get 60 Hz on the 13-inch over MST in Windows just fine from what I've read...

Nice setup! Yeah it turns out it really is SST, primary source right from AMDRadeon:

https://twitter.com/Thracks/status/456493341345984512

Yeah... that is what Apple says, but I think they're just ignoring the UD590 since it's not in their list of "supported displays." When that was written there weren't any Apple "supported" displays on the market with 60 Hz over SST!

That being said, others have reported the Samsung display to work at 60 Hz on the 2013 15-inch rMBP and the 2013 Mac Pro, so SST must be working on DisplayPort 1.2 equipped macs at 60 Hz...

Also, here's some further support for the refresh rate I'm getting on this machine if this makes you feel more comfortable!

Ah, interesting! Just out of curiosity, if you open switchresx what pixel clock do you get under Display Information? For the 13-inch I see 20-450 MHz listed as the range.