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VBudyn

macrumors newbie
Original poster
Jun 17, 2022
4
0
I recently bought a 16" M1 MBP. My plan was to sell my iMac Pro and use the money to buy a nice display. Alas, selling such an expensive machine locally is not easy (I'm not willing to run a gauntlet of eBay fraudsters), so it looks like I will be stuck with it. I have Monterey 12.4 running on both machines, and with Universal Control I can now seamlessly use the same mouse & keyboard to control both. That's fine, but there are occasions when it makes sense to extend my MBP's display (connected to Pro Display XDR), for example when I am in Lightroom or Photoshop. This is doable using AirPlay, but Apple in it's infinite wisdom (I'm being sarcastic) decided that when using an iMac as a secondary AirPlay display, the iMac's resolution is limited to 3840x2160 (where all the interface elements are tiny) or to low res 2560x1440. Now before someone tells me that this is a limitation of AirPlay, consider that when used in a mirror mode over AirPlay the iMac is able to duplicate my main display in native 5K resolution just fine !!! Clearly there is no technical reason why this is not possible in extend mode. There must be some hidden software switch that Apple decided to turn off in order to nudge owners of old iMacs toward bying an Apple display (Studio or Pro XDR). Greedy ba$tard$! If anyone knows how to flip that switch, I and all others who are in my situation will be eternally grateful.
 

Aiwi

macrumors member
Oct 21, 2010
83
73
Yeah it's a bummer. But there are options out there. A free option is to use an app like BetterDummy to create a fake external display on the MacBook, then use the built in macOS Screen Sharing app (on your iMac) to connect to the fake monitor. It will offer the full retina resolution.

I have both of my computers (the iMac and Macbook) connected using ethernet cables doing this.


I have also tried the Astropad Luna Display dongle, but I don't think it works any better than the free solution just mentioned above.
 

VBudyn

macrumors newbie
Original poster
Jun 17, 2022
4
0
A free option is to use an app like BetterDummy to create a fake external display on the MacBook, then use the built in macOS Screen Sharing app (on your iMac) to connect to the fake monitor. It will offer the full retina resolution.
Thanks. I'm a bot hesitant to use unsigned software. Still hoping Apple will flip on the AirPlay extend mode switch in the next OS release this Fall.
 

kvic

macrumors 6502a
Sep 10, 2015
516
459
A free option is to use an app like BetterDummy to create a fake external display on the MacBook, then use the built in macOS Screen Sharing app (on your iMac) to connect to the fake monitor. It will offer the full retina resolution.

I have both of my computers (the iMac and Macbook) connected using ethernet cables doing this.

This is a clever trick.

I wonder how well motion pictures perform. Such as maximising/minimising windows, scrolling long webpages..any stuttering, latency or cpu spikes?
 

Nguyen Duc Hieu

macrumors 68030
Jul 5, 2020
2,929
970
Ho Chi Minh City, Vietnam
I recently bought a 16" M1 MBP. My plan was to sell my iMac Pro and use the money to buy a nice display. Alas, selling such an expensive machine locally is not easy (I'm not willing to run a gauntlet of eBay fraudsters), so it looks like I will be stuck with it. I have Monterey 12.4 running on both machines, and with Universal Control I can now seamlessly use the same mouse & keyboard to control both. That's fine, but there are occasions when it makes sense to extend my MBP's display (connected to Pro Display XDR), for example when I am in Lightroom or Photoshop. This is doable using AirPlay, but Apple in it's infinite wisdom (I'm being sarcastic) decided that when using an iMac as a secondary AirPlay display, the iMac's resolution is limited to 3840x2160 (where all the interface elements are tiny) or to low res 2560x1440. Now before someone tells me that this is a limitation of AirPlay, consider that when used in a mirror mode over AirPlay the iMac is able to duplicate my main display in native 5K resolution just fine !!! Clearly there is no technical reason why this is not possible in extend mode. There must be some hidden software switch that Apple decided to turn off in order to nudge owners of old iMacs toward bying an Apple display (Studio or Pro XDR). Greedy ba$tard$! If anyone knows how to flip that switch, I and all others who are in my situation will be eternally grateful.

I would just buy a 4k display, and take some time to sell the iMac Pro, rather than relying on the unreliable Apple's mercy for such function.
 

VBudyn

macrumors newbie
Original poster
Jun 17, 2022
4
0
I would just buy a 4k display, and take some time to sell the iMac Pro, rather than relying on the unreliable Apple's mercy for such function.

I don't want to buy some cheap 4K display. I want to get a Studio Display or better (a nice 4K unit from Eizo, for example), and this isn't going to happen before I sell the iMac Pro. It has already sold 5 times on eBay over the past 6 weeks, each time to some shady character who wanted it shipped (even though listing clearly stated that computer is for local pickup only) and who wanted to pay outside of eBay. As for Apple, they will buy the machine back for $800 -- what a joke! If can't net at least $2500 for it, I'm just going to hold on to it and ride it until it dies. It is still almost as fast as my top of the line 16" MBP, so even if I can't use it as a 5K display, I can at least run it side by side with my MBP without having to use a separate mouse and keyboard.
 

Moonjumper

macrumors 68030
Jun 20, 2009
2,741
2,909
Lincoln, UK
In the early days of 5K iMac displays, the DisplayPort or HDMI bandwidth wasn't enough to support 5K displays, but the old Target Display Mode was never updated to support 5K when the interface options got better.

A common thought is Apple never made the change to force customers to buy newer Macs. But I have stayed with an older iMac instead of upgrading. If my iMac could be an external monitor for a newer Mac, I would have upgraded. Instead I am hanging onto my old iMac. I believe I am not the only one to follow that path.
 

chikorita157

macrumors 6502
Mar 8, 2019
284
439
Germantown, MD
If you are adventurous enough, you can gut your iMac 5K and get a control board that is compatible with your display and use it as a monitor. Someone done this already:


But given the iMac Pro is expensive, I wouldn’t do it. Maybe if you had a regular 5K iMac, it would be an option.

The short answer is, Thunderbolt 2/3 is not enough to do Target Display mode, especially at 5K, so it doesn’t exist.
 

VBudyn

macrumors newbie
Original poster
Jun 17, 2022
4
0
I just traded mine in with Apple when I purchased a Studio Mac. Prices have dropped, but I got $3K in trade in value.

Your original configuration must have been $8K+. I have a "lowly" 10 core with 64GB RAM and a 2TB SSD.
 
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