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bunnicula

macrumors 68040
Original poster
Jul 23, 2008
3,816
817
Anyone heard yet if this is going to be allowed on these new iMacs? Not the Pro, mind you. I'm looking at the 27" Retina 5K model.
 
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kelvin_chan

macrumors newbie
Jun 5, 2017
10
3
I have talked to several specialist from Apple.com Chat... they all think that the target display mode is enabled on the latest 2017 iMac. But I am not sure if they have the correct info... I am planning to check on this in person at Apple Store later today.
 

bunnicula

macrumors 68040
Original poster
Jul 23, 2008
3,816
817
I have talked to several specialist from Apple.com Chat... they all think that the target display mode is enabled on the latest 2017 iMac. But I am not sure if they have the correct info... I am planning to check on this in person at Apple Store later today.

Excellent! Please let me know what you find out. :)
 

redheeler

macrumors G3
Oct 17, 2014
8,419
8,841
Colorado, USA
I'm going to guess no on this one. Not a feature that Apple is in a hurry to bring back, useful though it may be.

But we'll see - I use it quite a bit on my old Mid 2010 iMac which works fine with non-Thunderbolt Macs (such as the classic Mac Pro), and Target Display Mode really does make that iMac more useful in its old age.
 
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nyc2pdx

macrumors 6502
Oct 20, 2012
292
165
Portland, Oregon
I was advised by Apple support that you can use the Thunderbolt 3 to Thunderbolt adapter and use target display on another iMac...provided it is thunderbolt technology. According to the support person, he checked with someone higher up (he could be feeding me a line, but that doesn't sound like Apple to me) and confirmed the 2017 iMac does allow for target display....just make sure the target display is thunderbolt!

With that, I will need to retire my 2009 iMac. Been using it in target display with my 2012 iMac utilizing the thunderbolt port, and the miniDisplayPort on my 2009 iMac. It's been a good run, first iMac. Time to go to that Apple Store in Boca.
 
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Chancha

macrumors 68020
Mar 19, 2014
2,094
1,895
I am not confident that target display mode will work, since on the previous 5K iMacs it was found out that the screen needed two streams of DP signals, being fed directly from the GPU via internal non-standard circuitry in a duplex manner for the full 5K 60Hz to be realized. Even with Thunderbolt 3, the MBP connecting to the LG Ultrafine 5K used similar tricks, but this time over a singular TB cable, since the intel TB3 specs only use DP 1.2 where a single DP connection does not have enough bandwidth for full 5K 60Hz. LG and Apple was probably on some hardware tricks to allow 2 streams of DP going through that one TB3 cable, treating them as data than DP streams.

If Apple were to allow the same to happen with the new iMac, specially to allow duplex DP1.2 to enter the motherboard to be fed to the panel(s), it actually should take substantial amount of engineering in circuitry and probably something more on firmware / OS level for that to happen.

Therefore, my guess is that if Target Display Mode is enabled, it won't be full 5K 60Hz, in which case Apple is likely to just not allow TDM at all.
 

rkuo

macrumors 65816
Sep 25, 2010
1,203
807
I am not confident that target display mode will work, since on the previous 5K iMacs it was found out that the screen needed two streams of DP signals, being fed directly from the GPU via internal non-standard circuitry in a duplex manner for the full 5K 60Hz to be realized. Even with Thunderbolt 3, the MBP connecting to the LG Ultrafine 5K used similar tricks, but this time over a singular TB cable, since the intel TB3 specs only use DP 1.2 where a single DP connection does not have enough bandwidth for full 5K 60Hz. LG and Apple was probably on some hardware tricks to allow 2 streams of DP going through that one TB3 cable, treating them as data than DP streams.

If Apple were to allow the same to happen with the new iMac, specially to allow duplex DP1.2 to enter the motherboard to be fed to the panel(s), it actually should take substantial amount of engineering in circuitry and probably something more on firmware / OS level for that to happen.

Therefore, my guess is that if Target Display Mode is enabled, it won't be full 5K 60Hz, in which case Apple is likely to just not allow TDM at all.
There are no tricks with TB3 and 5K ... dual displayport 1.2 streams are part of the spec. The new iMac already has TB3 built in, the question is whether Apple bothered to wire everything up. The part that seems very unlikely is for the new iMac to operate as a dual cable 5K monitor, similar to the Dell and HP 5K monitors.
 

fokmik

Suspended
Oct 28, 2016
4,909
4,688
USA
yep, 5k imac can act as a display. (tested in apple store) You need a tb3 cable that connects to a 15" MBP to the current imacs, or if you have the 13" you need to connect to 1 from the left side, the 2 tb3 from the right are not working
 
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Chancha

macrumors 68020
Mar 19, 2014
2,094
1,895
yep, 5k imac can act as a display. (tested in apple store) You need a tb3 cable that connects to a 15" MBP to the current imacs, or if you have the 13" you need to connect to 1 from the left side, the 2 tb3 from the right are not working
Thanks, this is really great news. May I ask if you tried to confirm if the display was definitely running at full 5K 60Hz?
 

mlody

macrumors 68000
Nov 11, 2012
1,592
1,220
Windy City
yep, 5k imac can act as a display. (tested in apple store) You need a tb3 cable that connects to a 15" MBP to the current imacs, or if you have the 13" you need to connect to 1 from the left side, the 2 tb3 from the right are not working

will the target display mode on new iMac's work with older laptops which only have Display Port, or even Windows system with Display Port?
 

fokmik

Suspended
Oct 28, 2016
4,909
4,688
USA
i tested only with TB3 <-> TB3 ports that have 40g bandwidth like left ports from 13" MBP or any from the 15" MBP
So i guess since older laptops dont have that bandwidth, will not work
 
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Criscoso

macrumors newbie
Jan 30, 2010
22
0
I'm waiting for target display mode since the first 5K 27-inch iMac release.
I work at home at least two days a week, and in my corp we use HP Windows laptops, so the target display mode is a must for me (I can't have two desks).
Can anyone comfirm target display mode will work, don't care if at 5K or not, using a Windows PC with a displayport?
Or there is any possibiity to use eGPU API to achieve something similar?
 

guibo

macrumors member
Jun 8, 2017
64
21
it's very unlikely target display mode works with a PC. the last gen of imacs that had the feature can only be driven by another mac that supports it. unless apple changed something, target display mode does not exactly convert the imac into a dumb monitor. there is a bit more going on than that.
 

Takuro

macrumors 6502a
Jun 15, 2009
573
261
yep, 5k imac can act as a display. (tested in apple store) You need a tb3 cable that connects to a 15" MBP to the current imacs, or if you have the 13" you need to connect to 1 from the left side, the 2 tb3 from the right are not working
That's good news. I wonder if this adds any plausibility for future eGPU support on the internal display. In other words, have something similar to target display mode but while the iMac is actually booted into MacOS, such that the display is kind of emulating the role of an external monitor for the iMac internals / eGPU.
 

bluespark

macrumors 68040
Jul 11, 2009
3,090
3,996
Chicago
it's very unlikely target display mode works with a PC. the last gen of imacs that had the feature can only be driven by another mac that supports it. unless apple changed something, target display mode does not exactly convert the imac into a dumb monitor. there is a bit more going on than that.

That's not correct. I routinely use my 2011 as a "dumb monitor" for a Windows PC with a mini display port. Of course, I have no idea whether the new iMacs will do this.
 

guibo

macrumors member
Jun 8, 2017
64
21
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