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2018 5k iMac as display for M1 Max MBP

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bradmwolf

macrumors newbie
Original poster
Feb 5, 2022
2
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Hey everyone. First time poster/long time lurker here. Sorry if this has been covered before but all of the research I’ve done seems very convoluted.

I’m looking to purchase a new MBP M1 Max. I’d like to use my 2018 5k iMac on Monterey as a display. Great display! Performance…meh.

So can I use my iMac as a display for a new MBP M1 Max?
 
Nope, Target Display Mode was deprecated for iMacs after 2014. Better to sell the iMac while you can still get something for it and buy a good monitor.
 
Right. I know target display mode is only for 2014 and earlier iMacs. I was under the impression that with the new OS/M1 being released, this may a possibility. Am I wrong?
 
Maybe you can convert the iMac into a display?
https://forums.macrumors.com/threads/diy-5k-monitor-success.2253100/
But I don't know if you could use that newly created display as a display for the iMac (so that the iMac is still usable). Can an iMac be booted if it's built-in display is no longer connected - as long as there's a display connected to its Thunderbolt ports?

If the iMac's display could be made to be connected to its Thunderbolt ports, then it could be possible to create some software that works like Thunderbolt Target Display Mode - to connect the display to another Mac using Thunderbolt. But I don't know if the M1 Mac's Thunderbolt controller can be programmed like the Intel Thunderbolt controllers.
 
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Any other solution would be software based - such as Lunar Display. https://astropad.com/luna-display-5-1/
Software solutions must compress the video to transmit it to the other computer so it won't behave like it was connected directly to the GPU like a Thunderbolt display would (or Thunderbolt Target Display Mode).
 
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joevt said:
Any other solution would be software based - such as Lunar Display. https://astropad.com/luna-display-5-1/
Software solutions must compress the video to transmit it to the other computer so it won't behave like it was connected directly to the GPU like a Thunderbolt display would (or Thunderbolt Target Display Mode).
Click to expand...

This may be a better option when we're all on 2.5 GB Ethernet.

GB Ethernet is slightly laggy with QHD. I have not tried it with 4k but I suspect it would be worse and 5k, even worse. It may not be bad for smaller windows but you don't get the feeling that you are working directly from the machine. You can buy 2009 and 2010 iMacs for $50-$100 if you are patient and you get a nice QHD 27 inch monitor and nice speakers. I'm typing on such a system myself. I'm actually using the system as a computer, though, not as a display.

So, perhaps run office stuff off the iMac itself and then screen share into the M1 Max for your high-performance stuff. If this is video-editing, though, it likely won't work. I wanted to do something like this but wound up just using the M1 Pro as a mobile device and having a separate desktop solution altogether. It is nice to use the MacBook Pros in both desktop and mobile modes but it's easier to keep them separate. I do have a nice USB-C monitor that I can use if I need to turn it into a desktop.
 
theluggage said:
How about using Thunderbolt?

I don't mean trying to use the iMac as a Thunderbolt display, I mean using Thunderbolt Bridge to set up an 10G+ IP network link between the two Macs (https://www.macworld.com/article/223179/connecting-two-macs-using-thunderbolt.html).

Anybody tried Luna display or similar over such a link?
Click to expand...

I have not tried using multiple networks on one system and it's an interesting idea. Being able to use old 5k iMacs as monitors would be great as you can get them for as little as $400 these days. I expect them to drop further after Apple Silicon comes out.
 
I am using the built in Screen Sharing with thunderbolt cable and thunderbolt 3 to 2 adapter as a local network between my M1 Mac Mini and iMac 2011, but you can use an Ethernet cable with the same results. A cheap 4k headless HDMI adapter is needed for graphics acceleration, I got mine for around £5 from amazon with really great results. It has just a very little bit of jitter once in a while even on full quality @ 1440p. Don't get me wrong it is not quite the same as TDM but it is very usable as a second display (around 30fps).

It has the added bonus of being able to have the display in a window or full screen, drag and drop files and folders between the 2 computers and a shared keyboard, mouse and trackpad.
 
pshufd said:
I have not tried using multiple networks on one system and it's an interesting idea. Being able to use old 5k iMacs as monitors would be great as you can get them for as little as $400 these days. I expect them to drop further after Apple Silicon comes out.
Click to expand...
Luna certainly list it as an option. The downside would be that it would tie up two Thunderbolt ports - one for networking, another for the luna dongle (which I'm guessing is just a 'dummy load' to fool the Mac into thinking it has two displays attached).

I don't suppose that Apple's Sidecar supports mac-to-mac?
 
carl varley said:
I am using the built in Screen Sharing with thunderbolt cable and thunderbolt 3 to 2 adapter as a local network between my M1 Mac Mini and iMac 2011, but you can use an Ethernet cable with the same results. A cheap 4k headless HDMI adapter is needed for graphics acceleration, I got mine for around £5 from amazon with really great results. It has just a very little bit of jitter once in a while even on full quality @ 1440p. Don't get me wrong it is not quite the same as TDM but it is very usable as a second display (around 30fps).

It has the added bonus of being able to have the display in a window or full screen, drag and drop files and folders between the 2 computers and a shared keyboard, mouse and trackpad.
Click to expand...

It sounds like it isn't that hard to set up a LAN. I'm just using the iMacs as iMacs for now. At some point in the future, though, I may look into screen sharing over a Thunderbolt LAN.
 
pshufd said:
It sounds like it isn't that hard to set up a LAN. I'm just using the iMacs as iMacs for now. At some point in the future, though, I may look into screen sharing over a Thunderbolt LAN.
Click to expand...
The thunderbolt version is quite expensive at around £80. I just had both the cable and adapter already. Using a ethernet cable yields very similar results at a fraction of the cost at probably around £10. This is if you don't already have both a cable and adapter. If you do go down this route make sure you are not connected via wifi by turning it off before you try to connect. It's quite a poor experience.
 
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