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curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
For my own use, I researched and successfully tested methods of integrating an M1 Mac mini with a Thunderbolt Display and up to to two iMacs in Target Display Mode. My focus was on minimizing expense since both my Late 2009 iMac and Thunderbolt Display are aging. So I've identified low cost interface items that are currently available on Amazon. For a single iMac, the interface items are less than $40. For the Thunderbolt Display, the cost is < $50. The attached PDF should make clear how to get this done. You can go all out with three displays or just one. Note that you can use only one of the M1 Mini's Thunderbolt ports for a display unless you turn to something like a DisplayLink adapter. The options I've included are focused on employing existing Apple screens that you may already own and they should not add additional calculation burden on the CPU in the way DisplayLink appears to. Some of this should be applicable to M1 laptops and I hope this helps someone!
 

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curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
I forgot to mention that I tested with Big Sur 11.0.1 and that if you have enabled screen sharing on the iMac, you will be able to run its applications using the Apple Screen Sharing app on the Mac mini. This is almost like having a fourth screen with the swipe of the trackpad. That's a pretty cools capability if you're using the old iMac as a file server or for legacy apps.
 
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4sallypat

macrumors 68020
Sep 16, 2016
2,230
1,907
So Calif
Very cool way to use your older iMac as a target display.

I already use the Apple 27" TB display via TB3-TB2 adapter = do you know if I can connect 2 Apple 27" TB displays instead of using the iMac ?
 

curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
Very cool way to use your older iMac as a target display.

I already use the Apple 27" TB display via TB3-TB2 adapter = do you know if I can connect 2 Apple 27" TB displays instead of using the iMac ?
I don't THINK that is currently possible. It seems like Apple have designed the M1 Mini GPU to support two external displays with one permanently allocated to the HDMI port and the other to either of the Thunderbolt ports. People are getting additional displays to work with external graphics hardware (i.e. DisplayLink HDMI or DisplayLink DisplayPort) driven by the USB-C ports, but I don't think those will drive your second TB Display. You could originally daisy chain a second TB display using the port on the back of the first. But I think that if you do that with the M1 you will probably get one working and the second with a black screen. You should definitely try it though if you have the cables and report back! :)
 
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bryguym

macrumors newbie
Dec 19, 2020
3
1
Seattle, WA
I've tried 1a with a iMac (27-inch, Mid 2011) and I can't seem to get it to go. Do you have to hit any buttons, such as Command F2 to enter Target display mode?
 

curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
I don't think you're going to get 1A to work for you because your port on a 2011 iMac is a Thunderbolt port. So it's not going to work with a DisplayPort cable. I believe you will have to do something more LIKE 1B but you will have to add a thunderbolt 2 cable where the blue line is shown. So you will end up with a Thunderbolt 3/2 adapter and a Thunderbolt 2 cable. I strongly recommend you buy those both from Apple to avoid a lot of hassle - unless you can find a specific cable someone has tested. Then once connected, yes you will have to have a keyboard attached to the iMac and invoke Cmd F2. You may need to invoke it repeatedly to get it going. Here are two articles on TDM. One how to, and another from Apple. Note that Apple says that you must have MacOS High Sierra or earlier on the iMac used as a display, however my Late 2009 iMac has a patched version of Mojave, so your results may vary. I suspect the guys doing the patch bypassed whatever was disabled. Good Luck to you!


These are key points from Apple's doc:

Target display mode requires macOS High Sierra or earlier on the iMac used as the external display. It does not work with macOS Mojave or later.
 

curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
For my own use, I researched and successfully tested methods of integrating an M1 Mac mini with a Thunderbolt Display and up to to two iMacs in Target Display Mode. My focus was on minimizing expense since both my Late 2009 iMac and Thunderbolt Display are aging. So I've identified low cost interface items that are currently available on Amazon. For a single iMac, the interface items are less than $40. For the Thunderbolt Display, the cost is < $50. The attached PDF should make clear how to get this done. You can go all out with three displays or just one. Note that you can use only one of the M1 Mini's Thunderbolt ports for a display unless you turn to something like a DisplayLink adapter. The options I've included are focused on employing existing Apple screens that you may already own and they should not add additional calculation burden on the CPU in the way DisplayLink appears to. Some of this should be applicable to M1 laptops and I hope this helps someone!
 

curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
My original post is for iMacs that have DisplayPort video ports. I apologize that I wasn't clearer about that. If your iMac is 2011 to mid 2014, it has a Thunderbolt port and you will not get Target Display Mode working with a DisplayPort cable. You will need to use a Thunderbolt solution.
 

bryguym

macrumors newbie
Dec 19, 2020
3
1
Seattle, WA
Ah, got it. Thank you for your help. I do have a thunderbolt 2 to thunderbolt 3 setup. It works with Target display mode between my 2019 macbook pro and the mid 2011 27" imac, but I can't seem to get it to go between the m1 mac mini and the mid 2011 27" imac. Any ideas there?
 
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curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
Hmm... I don't know what would cause that unless you already have a display on one of the thunderbolt ports. You will NOT get two thunderbolt displays to work via the two USB-C ports. People are getting DisplayLink adapters to work on those though. A single Thunderbolt solution should work - except possibly for that Apple caveat about having an older OS on the iMac. The only thing I can think to recommend is detaching the cables from both machines, reattaching, and then doing the Cmd F2 thing repeatedly to see if it will fall in line. If that fails, there is still option 3 though that's a little more pricey. It does provide full resolution at the full display rate. My current dual display setup consists of those shown in Figuers 1B and 2, but I did try Fig. 3 and it worked great.
 

Deccr

macrumors member
Nov 29, 2020
56
37
Unfortunately Target Display mode does not work on Thunderbolt iMacs with M1 devices.


It will work with older iMacs (pre-2011) which support Target Display mode via a mini DisplayPort, which confusingly has the same size and shape connector as Thunderbolt 1/2.

I have a 2011 27 iMac and M1 Mac mini so can confirm this combination does not work.

However, there are some options I’m looking at:

1, Buy a dummy HDMI plug: https://www.amazon.co.uk/dp/B087QDCZ4L/ref=cm_sw_r_cp_awdb_imm_t1_wbY3FbP35W05F?psc=1 - then use VNC (screen sharing) to access the M1 Mac from the iMac.

You can force the 4K dummy HDMI plug to 2560x1440, to match the 2011 iMac resolution. I’ve got one and managed to do this, obviously screen sharing isn’t perfect but a workaround. You can use a USB-C -> DisplayPort or HDMI adapter to get a 2nd monitor connected.

2, Buy a Luna Display USB-C dongle: https://shop.astropad.com/ I’ve ordered one and will give this a go, with the Mac-to-Mac mode. Still waiting on delivery for now.

Again you can use the HDMI port on the mini to connect a 2nd monitor.

3, Extreme but potentially the best option (if you can give up your iMac as a useable computer?): get something like this - https://www.ebay.co.uk/itm/HDMI-DVI...-2560-1440-LM270WQ1-SD-E2-panel-/193390883105

Teardown the iMac and install the driver board to the iMac display. This will give you direct HDMI/DisplayPort/DVI inputs for the iMac display - essentially turning the iMac into a ‘dumb’ monitor - but allowing *any* device to connect and display an image.

These are all workarounds and not ideal - you may find buying a monitor the best option.

Although I’m sorely tempted by those who have made their own 5K iMac monitor - using option 3 with the appropriate 5K screen, driver board and old iMac case. Not cheap - but would give a beautiful 5K monitor.

(Search for ‘Secret Apple 5K display’ - there’s a Reddit thread and YouTube video explaining how it’s done)

EDIT: Removed Reddit 5K monitor info
 
Last edited:

sheepman

macrumors newbie
Jan 12, 2021
1
0
Unfortunately Target Display mode does not work on Thunderbolt iMacs with M1 devices.


It will work with older iMacs (pre-2011) which support Target Display mode via a mini DisplayPort, which confusingly has the same size and shape connector as Thunderbolt 1/2.

I have a 2011 27 iMac and M1 Mac mini so can confirm this combination does not work.

However, there are some options I’m looking at:

1, Buy a dummy HDMI plug: https://www.amazon.co.uk/dp/B087QDCZ4L/ref=cm_sw_r_cp_awdb_imm_t1_wbY3FbP35W05F?psc=1 - then use VNC (screen sharing) to access the M1 Mac from the iMac.

You can force the 4K dummy HDMI plug to 2560x1440, to match the 2011 iMac resolution. I’ve got one and managed to do this, obviously screen sharing isn’t perfect but a workaround. You can use a USB-C -> DisplayPort or HDMI adapter to get a 2nd monitor connected.

2, Buy a Luna Display USB-C dongle: https://shop.astropad.com/ I’ve ordered one and will give this a go, with the Mac-to-Mac mode. Still waiting on delivery for now.

Again you can use the HDMI port on the mini to connect a 2nd monitor.

3, Extreme but potentially the best option (if you can give up your iMac as a useable computer?): get something like this - https://www.ebay.co.uk/itm/HDMI-DVI...-2560-1440-LM270WQ1-SD-E2-panel-/193390883105

Teardown the iMac and install the driver board to the iMac display. This will give you direct HDMI/DisplayPort/DVI inputs for the iMac display - essentially turning the iMac into a ‘dumb’ monitor - but allowing *any* device to connect and display an image.

These are all workarounds and not ideal - you may find buying a monitor the best option.

Although I’m sorely tempted by those who have made their own 5K iMac monitor - using option 3 with the appropriate 5K screen, driver board and old iMac case. Not cheap - but would give a beautiful 5K monitor.

(Search for ‘Secret Apple 5K display’ - there’s a Reddit thread and YouTube video explaining how it’s done)

EDIT: Removed Reddit 5K monitor info
Any update on this? Curious how I should move forward.
 

germzz

macrumors newbie
Jan 28, 2021
3
0
Does anyone know if the target display mode will work on the M1 MacBook Air?
 

curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
Does anyone know if the target display mode will work on the M1 MacBook Air?
Oh good idea. I haven‘t tried that But I will. I will try to test that by this time tomorrow (Friday the 29th).
 

curtc757

macrumors newbie
Original poster
Dec 10, 2020
11
11
Thank you for doing that! I do hope this could work!
It worked perfectly first time for me. Be aware of two things though:

1) I am using a Late 2009 iMac that had a mini DisplayPort. Newer iMac models have a Thunderbolt port and others have said that does not work. I have no way to verify. Note carefully the symbol designating which port the iMac is equipped with because the physical connector may look identical.

2) This connection will not power your MacBook Air. You’ll need The second USB4/Thunderbolt port for that.

I‘ve included a photo of the specific cable used which has limited availability on Amazon. Your results may vary with other cables.
 

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BeatCrazy

macrumors 68040
Jul 20, 2011
3,049
1,837
It worked perfectly first time for me. Be aware of two things though:

1) I am using a Late 2009 iMac that had a mini DisplayPort. Newer iMac models have a Thunderbolt port and others have said that does not work. I have no way to verify. Note carefully the symbol designating which port the iMac is equipped with because the physical connector may look identical.

2) This connection will not power your MacBook Air. You’ll need The second USB4/Thunderbolt port for that.

I‘ve included a photo of the specific cable used which has limited availability on Amazon. Your results may vary with other cables.
Can you post the link the exact/working cable you used?
 

germzz

macrumors newbie
Jan 28, 2021
3
0
It worked perfectly first time for me. Be aware of two things though:

1) I am using a Late 2009 iMac that had a mini DisplayPort. Newer iMac models have a Thunderbolt port and others have said that does not work. I have no way to verify. Note carefully the symbol designating which port the iMac is equipped with because the physical connector may look identical.

2) This connection will not power your MacBook Air. You’ll need The second USB4/Thunderbolt port for that.

I‘ve included a photo of the specific cable used which has limited availability on Amazon. Your results may vary with other cables.
Thank you for testing, unfortunately, the iMac that I have is 2013. :(
 

Padamis

macrumors newbie
Feb 9, 2021
2
0
Unfortunately Target Display mode does not work on Thunderbolt iMacs with M1 devices.


It will work with older iMacs (pre-2011) which support Target Display mode via a mini DisplayPort, which confusingly has the same size and shape connector as Thunderbolt 1/2.

I have a 2011 27 iMac and M1 Mac mini so can confirm this combination does not work.

However, there are some options I’m looking at:

1, Buy a dummy HDMI plug: https://www.amazon.co.uk/dp/B087QDCZ4L/ref=cm_sw_r_cp_awdb_imm_t1_wbY3FbP35W05F?psc=1 - then use VNC (screen sharing) to access the M1 Mac from the iMac.

You can force the 4K dummy HDMI plug to 2560x1440, to match the 2011 iMac resolution. I’ve got one and managed to do this, obviously screen sharing isn’t perfect but a workaround. You can use a USB-C -> DisplayPort or HDMI adapter to get a 2nd monitor connected.

2, Buy a Luna Display USB-C dongle: https://shop.astropad.com/ I’ve ordered one and will give this a go, with the Mac-to-Mac mode. Still waiting on delivery for now.

Again you can use the HDMI port on the mini to connect a 2nd monitor.

3, Extreme but potentially the best option (if you can give up your iMac as a useable computer?): get something like this - https://www.ebay.co.uk/itm/HDMI-DVI...-2560-1440-LM270WQ1-SD-E2-panel-/193390883105

Teardown the iMac and install the driver board to the iMac display. This will give you direct HDMI/DisplayPort/DVI inputs for the iMac display - essentially turning the iMac into a ‘dumb’ monitor - but allowing *any* device to connect and display an image.

These are all workarounds and not ideal - you may find buying a monitor the best option.

Although I’m sorely tempted by those who have made their own 5K iMac monitor - using option 3 with the appropriate 5K screen, driver board and old iMac case. Not cheap - but would give a beautiful 5K monitor.

(Search for ‘Secret Apple 5K display’ - there’s a Reddit thread and YouTube video explaining how it’s done)

EDIT: Removed Reddit 5K monitor info
Deccr,
Hello, did the Luna Display Dongle USB C work for you? I have the same setup as you and wasn’t sure if I should go with option 1 or 2. Thanks
 

Deccr

macrumors member
Nov 29, 2020
56
37
The Luna Display does work well, however I have ended up replacing the iMac with a new monitor.

If you're not sure, you could buy a dummy plug, test it out and return it if you're not happy with it? It's a smaller investment than the Luna Display.
 

Padamis

macrumors newbie
Feb 9, 2021
2
0
The Luna Display does work well, however I have ended up replacing the iMac with a new monitor.

If you're not sure, you could buy a dummy plug, test it out and return it if you're not happy with it? It's a smaller investment than the Luna Display.
I got the screen sharing method to work on the IMac at full resolution when I had the mini plugged into a 4K tv with the HDMI port simultaneously. However when I disconnect the hdmi cable the resolution to the iMac drops and can’t go full screen. Hoping the dummy plug that’s coming tomorrow will fix that. Thanks for the solution, I bought a cheap second hand IMac 27 after reading in several places , Apple included , that it would work as a display only to find it wouldn’t.
 
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