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Naive iMac 5K display question

jamesjingyi

jamesjingyi

macrumors 6502a
Original poster
Dec 20, 2011
853
164
UK
Hi guys!

So here's my question for today. Why can't you use the retina iMac 5K as a display using two thunderbolt connections instead of one? You could just map the screen as 2x 2560x1440 displays and then sorta stitch them together couldn't you? I mean you can run dual 4K monitors with Thunderbolt so surely this is possible?

If I am being very stupid, please tell me.
 
jamesjingyi said:
Hi guys!

So here's my question for today. Why can't you use the retina iMac 5K as a display using two thunderbolt connections instead of one? You could just map the screen as 2x 2560x1440 displays and then sorta stitch them together couldn't you? I mean you can run dual 4K monitors with Thunderbolt so surely this is possible?

If I am being very stupid, please tell me.
Click to expand...

Yes, it would be technically possible. But Apple made it physically impossible.

Hopefully in the future someone finds a way to hack the firmware to do that, or Apple allows it, but i wouldn't hold my breath.
 
boast said:
Yes, it would be technically possible. But Apple made it physically impossible.

Hopefully in the future someone finds a way to hack the firmware to do that, or Apple allows it, but i wouldn't hold my breath.
Click to expand...

So I'm not being crazy, it is possible it just isn't very elegant because it requires two cables instead of one. I seem to remember that they had to do this with the 30" Cinema display.

Is there a standard that allows 5K displays to work?
 
jamesjingyi said:
You could just map the screen as 2x 2560x1440 displays and then sorta stitch them together couldn't you?
Click to expand...

You realize that 5K is still twice as many pixels as 2x 1440p displays, right?

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boast said:
Yes, it would be technically possible. But Apple made it physically impossible.

Hopefully in the future someone finds a way to hack the firmware to do that, or Apple allows it, but i wouldn't hold my breath.
Click to expand...

You don't know that there isn't a technical limitation behind it, do you.
 
Naive iMac 5K display question

As I understand it, the limitation is on the 5K iMac firmware/software itself, not Thunderbolt 2/DP 1.2.

Bottom line; the 2014 5K iMac does not support TDM, at all. It never will, unless someone makes a hack.
 
redheeler said:
You realize that 5K is still twice as many pixels as 2x 1440p displays, right?
Click to expand...

OOH MY MATHS IS TERRIBLE! Its 4x isn't it?

The retina iMac is 5120x2880, means the height and width doubles from 2560x1440, meaning there are 4x the amount of pixels...

Having said that, 5K has 14.7 million pixels and 4K has 8.8 million. 2x 8.8 million is still a lot more than 14.7 so theoretically it should work? Just output two 2880x2560 displays..

(btw thanks for the correction, I get stupid sometimes :D)

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Maybe when they release the 5K cinema display, they will have a better solution. I think its gonna be disappointing that the first lot with the gen 1 nMP and riM will miss out on interconnectivity though...
 
There is still NO..

jamesjingyi said:
OOH MY MATHS IS TERRIBLE! Its 4x isn't it?

The retina iMac is 5120x2880, means the height and width doubles from 2560x1440, meaning there are 4x the amount of pixels...

Having said that, 5K has 14.7 million pixels and 4K has 8.8 million. 2x 8.8 million is still a lot more than 14.7 so theoretically it should work? Just output two 2880x2560 displays..

(btw thanks for the correction, I get stupid sometimes :D)

----------

Maybe when they release the 5K cinema display, they will have a better solution. I think its gonna be disappointing that the first lot with the gen 1 nMP and riM will miss out on interconnectivity though...
Click to expand...

...standard port taht has the bandwidth to run a 5 K screen from one port. The nMP can run one from 2 thunderbolt 2 ports using the 2 graphics cards. The Imac has a botched apple solution inside that is not connected through to the thunderbolt ports on it. This is why it cannot be used in target display mode.
 
Samuelsan2001 said:
...standard port taht has the bandwidth to run a 5 K screen from one port. The nMP can run one from 2 thunderbolt 2 ports using the 2 graphics cards. The Imac has a botched apple solution inside that is not connected through to the thunderbolt ports on it. This is why it cannot be used in target display mode.
Click to expand...

Apple doesn't want to use comprimise-based solutions like that Dell 5K monitor (which is, in fact, two monitors combined into one) because of certain issues that may arise. That's why they invested into a custom TCON. External 5K Apple Displays will come with Displayport 1.3 (which comes in 2016) and not sooner. Nothing to do with botched solutions. It's the proper way to do 5K.

----------
MacVidCards said:
Yes, especially since you can run the same exact panel as a Dell U2715K on any 2006-2012 cMP with a lowly GTX960 at full 5K. (via 2 @ DP cables)
Click to expand...

Dell U2715K is not the same exact panel, it is 2 panels combined into one with occasional graphical tearing as a result. It is not the same as the 5K screen in iMac. Doing 2-monitors-that-are-one is just not Apple's thing. They are waiting for Intel to do it the right way.
 
Samuelsan2001 said:
...standard port taht has the bandwidth to run a 5 K screen from one port. The nMP can run one from 2 thunderbolt 2 ports using the 2 graphics cards. The Imac has a botched apple solution inside that is not connected through to the thunderbolt ports on it. This is why it cannot be used in target display mode.
Click to expand...

Creating a whole new TCON so they don't have to half ass the engineering is "botched". :rolleyes:
 
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