Adding external monitors to my iMac

swiftaw

Member
SoSH Member
Jan 31, 2009
2,109
Since I am working from home a lot these days I need to dramatically increase my screen real-estate. I have a Late 2015 27" iMac 5K with the highest graphic card and I was thinking of buying 2 Dell U2720Q displays (3840x2160 each). The iMac has 2 Thunderbolt 2 ports with Mini DisplayPort output.

Obviously I want to make sure this will work before I buy them. The first question is how should I connect them. Since the monitors ship with a DisplayPort cables i thought I could pick up a couple of DisplayPort to Mini DisplayPort adapters to connect to the iMac. I am concerned that the monitor says it supports DisplayPort 1.1a or 1.4 whereas the iMac supports 1.2, so I may have to run the monitor in 1.1a mode which may impact performance. Alternatively I could buy HDMI to MiniDisplayPort adapters and connect that way.

SO I'm trying to figure out if either of the above connection methods will give me the full 3840x2160@60Hz on both monitors or whether I'll have issues, but I'm struggling to find any info when googling.

(I know there are other monitors out there but I'm eying the Dell because it also has a USB-C connector that i can use for my 2020 Macbook Air).
 

lars10

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SoSH Member
Jul 31, 2007
6,653

TenCentBeerNight

Member
SoSH Member
Jul 11, 2009
86
Oxford, UK
Since I am working from home a lot these days I need to dramatically increase my screen real-estate. I have a Late 2015 27" iMac 5K with the highest graphic card and I was thinking of buying 2 Dell U2720Q displays (3840x2160 each). The iMac has 2 Thunderbolt 2 ports with Mini DisplayPort output.

Obviously I want to make sure this will work before I buy them. The first question is how should I connect them. Since the monitors ship with a DisplayPort cables i thought I could pick up a couple of DisplayPort to Mini DisplayPort adapters to connect to the iMac. I am concerned that the monitor says it supports DisplayPort 1.1a or 1.4 whereas the iMac supports 1.2, so I may have to run the monitor in 1.1a mode which may impact performance. Alternatively I could buy HDMI to MiniDisplayPort adapters and connect that way.

SO I'm trying to figure out if either of the above connection methods will give me the full 3840x2160@60Hz on both monitors or whether I'll have issues, but I'm struggling to find any info when googling.

(I know there are other monitors out there but I'm eying the Dell because it also has a USB-C connector that i can use for my 2020 Macbook Air).
Not sure if this is helpful, but even though apple claims to support displayport 1.2 they don't support MST (multi-stream transport) as part of that. That means that you can't daisy chain displayport monitors together and will instead need to make a separate connection to each monitor.
 

swiftaw

Member
SoSH Member
Jan 31, 2009
2,109
Not sure if this is helpful, but even though apple claims to support displayport 1.2 they don't support MST (multi-stream transport) as part of that. That means that you can't daisy chain displayport monitors together and will instead need to make a separate connection to each monitor.
Yeah, I’d read that and thus am planning to connect to reach one separately.