Pbwj

macrumors member
Original poster
Oct 12, 2018
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I have the iMac (Retina 5K, 27-inch, Late 2014) and looking to find a second monitor that is 5k as well. I see that LG makes two 5k 27" monitors but not sure if it supports my Late 2014 iMac because there isn't a thunderbolt 3 port. Could someone point me in the right direction? Thanks

 

joevt

macrumors 68040
Jun 21, 2012
3,171
1,452
The 2014 iMac only has Thunderbolt 2 which only support DisplayPort 1.2 which only supports up to 4K 60Hz.

A 5K display will require a dual cable connection - the Dell UP2715K or HP Z27q or similar would be best.

You can't get 5K from the LG UltraFine 5K displays because they require two DisplayPort 1.2 signals over Thunderbolt. Thunderbolt 2 does not have enough bandwidth for two DisplayPort 1.2 signals. You could try connecting a Blackmagic eGPU (see the eGPU.io website for info about using eGPUs with Thunderbolt 2 Macs). The Blackmagic eGPUs are the only ones that allow connecting a Thunderbolt 3 display. The LG UltraFine 5K displays do not have a single cable 5K mode - they can work at 4K though.

If you connect an eGPU with a GPU that supports DisplayPort 1.4, then you can connect a single cable 5K display like the iiyama ProLite XB2779QQS-S1.

If you connect an eGPU with a GPU that supports DisplayPort 1.4 and DSC (like the W5700) then you can connect the Apple Pro Display XDR and get 6K using USB-C.

You can connect an LG UltraFine 5K to an externally powered Thunderbolt 3 add-in card that has two DisplayPort inputs, such as the GC-TITAN RIDGE or the GC-ALPINE RIDGE to get 5K using two DisplayPort 1.2 connections, but the add-in card has no PCIe connection to the computer, therefore you will not be able to use the USB features of the display, such as brightness control and USB ports.
 
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Talliwikboy

macrumors newbie
Jul 14, 2020
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@joevt I'm in a similar boat and looking for either a 4k or 5k display (to connect to an iMac 2014 5k). So, it seems that there is no way to connect up to a 5k display without both Display 1.2 ports being used. I've looked but can't seem to find any such 'dual display port 1.2 connectors to USB 3' type connectors ...? so assume they don't exist.

Also, lastly when I read online that Displayport 1.2 can handle 4k @ 60hz... is that FULL sized 4k? as in 4096 x 2160? I'm aware there are very few full sized monitors available but its unclear from my research whether display port 1.2. can handle fullsize?
 
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joevt

macrumors 68040
Jun 21, 2012
3,171
1,452
I've looked but can't seem to find any such 'dual display port 1.2 connectors to USB 3' type connectors ...? so assume they don't exist.
I said you can use a Thunderbolt 3 add-in card with two DisplayPort inputs such as the GC-TITAN RIDGE or GC-ALPINE RIDGE.

Also, lastly when I read online that Displayport 1.2 can handle 4k @ 60hz... is that FULL sized 4k? as in 4096 x 2160? I'm aware there are very few full sized monitors available but its unclear from my research whether display port 1.2. can handle fullsize?
4096x2304@60Hz uses a pixel clock of 605 MHz using CVT-RB timing calculation. That's well under the DisplayPort 1.2 max of 720 MHz required for 8 bpc RGB (max for 10 bpc RGB is 576 MHz). I think HDMI 2.0 4K resolutions (whether 4096 or 3840) all use 594 MHz which is under the HDMI 2.0 max of 600 MHz for 8 bpc RGB (10 bpc uses YCbCr 4:2:2 or 4:2:0).
 
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