Q: Dual 4k support for MacBook Pro Mid 2014

Are you sure two 4ks can be connected via Thunderbolt? I tried connecting a standard 4k (Asus) and a 2560*1440 monitor via Thunderbolt/DP, and one of the two always shuts down when I try to connect both. The only way to connect both is if I use DP on one, Thunderbolt on the other. I have a mid-2014 RMBP.

Hi,

I have 2 Dell UP2414Q 4K monitors on a Late 2013 Retina Macboo Pro 15-Inch.

I can

- Run both monitors at 4K on thunderbolt ports at 30Hertz

- Run ONE monitor at 4K 60 Hertz on Thunderbolt and the second at 4K 30 Hertz on HDMI (Current Config)

I can not

- Run 2 monitors at 60 Hertz

- Plug 2 monitors on Thunderbolt as soon as one monitor is at 60 Herz.

     The second thunderbolt port STOPS WORKING PERIOD.

If your 4K monitor is at 60 Hertz the second thunderbolt shuts down. Not enough bandwidth. !

Or said another way if the monitor is set to display port 1.2 (60 hertz) the second thunderbolt shuts down.

You would have have to check if the monitor firmware can be hard set NOT to use display port 1.2.

In my case I connect the second monitor to the HDMI port because I want to have the faster refresh rate.

So if I have the 4k monitor (UP2414Q) running at 60hz on one thunderbolt port, I won't be able to =run my Time Machine external drive off the other one? And you can't run 4k at 60z off the HDMI port?

Hugh

Thank you, Stephane! I set the DP on the Monitor to 1.1, 30 Hz refresh rate, second thunderbolt still shuts down.

Only another display on the second thunderbolt doesn't work (not even 1080p@60)  - I have one 4k@60Hz monitor on one port and other USB peripherals through the CalDigit Dock on the other.

I'm not sure why another display doesn't work, there should be enough bandwidth on the second port.

Hugh, you're right, according to my testing: Only one 4k display on thunderbolt, regardless if 30 or 60hz. I'm able to connect a second via hdmi, but only 30hz.

Which is absolutely fine for me - I only want a single external monitor. And can this run at the full 4k - i.e. 3840 x 2160.

The other question is: If I have that running at 3840 x 2160 on 1 thunderbolt port at 60 hz, can I run my external hard drive (with all my photographs on) off the other one.

Hugh

Hi Guys,

Just to confirm I was able to run TWO Dell 4K UP2414Q at 30 frames using BOTH Thunderbolt ports.

As soon as one of the monitors has DP 1.2 enabled the second Thunderbolt port shuts down.

That was on Mavericks. Haven't tried on Yosemite.

Thanks - Stephane - that's useful info!

That means, in theory,  in terms of bandwidth, I should be able to connect one 4k@60 and another 1080p@60 on thunderbolt, which is what I'd like to do.

@Hugh - any other peripheral, like a hard disk will work. Only the 2nd display doesn't work on thunderbolt, if the first display is using DP1.2 (needed for 4k@60)

Hi N4s33,

No! As soon as one monitor is 4K@60 the second Thunderbolt shuts down. Any other monitor must be connected via HDMI.

Yes I face this issue - I meant, it should work in theory right? There is enough bandwidth to support it _in theory_ - so this could be a software bug?

If DP1.2 is used, does it exclude HDMI connections  - or - does the protocol have any limiiation where regular displays no longer work?

Stephanie, do you really mean 'shut down'? I don't want a second monitor: what I want is proper 4k / 60 hz - i.e. the 3840 x 2160 from the Dell monitor from one thunderbolt and my TB hard drive from the second thunderbolt port. Will that work?

Hugh

No i in Stéphane

Great question. I could NOT get a second monitor to work on the second thunderbolt once I setup the first monitor at 60 Hertz.

(at 30 Hertz both thunderbolt port worked)

But since even a standard 1080p monitor would not work I would guess that a Thunderbolt HD would not work also.

I my case I use the USB3 hub in the monitor for external hard drives (Time machine and Movies).

Stéphane