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I have a 2012 iMac running Catalina and I'd like to use it as a secondary display to my MacBook Pro. I connected the two computers via a USB cable and hit both ⌘ CommandF2 and then tried ⌘ CommandFnF2. It's not working.

Do I need to use a Thunderbolt? Any input/advice would be most appreciated.

Allan
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Shannon Poulos
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  • This question is not a duplicate and the answer referenced above pertains to connecting a Microsoft Surface 4 to a 2019 iMac and not a MacBook Pro connected to a 2012 iMac as pertains to the questions above. – Gerard de Jong Aug 11 '20 at 17:12
  • Concur, this is NOT a duplicate. – James Brickley Aug 22 '20 at 19:38
  • @GerarddeJong If you read the answer, you’ll find that it’s canonical, meaning it applies to all situations and not limited to what’s in the question. This question is comprehensive and answered by that one. – Allan Aug 26 '20 at 08:23
  • Thank you @Allan but I respectfully disagree on account of the question pertaining to an entirely different platform (Microsoft vs. Mac), this question is about connecting different hardware i.e. a MacBook vs. a Surface Pro 4. I'm not the only person who things this should not be marked as a duplicate (as per the comment's above). Can we please have an un based third party make a call on this one. – Gerard de Jong Aug 26 '20 at 13:24
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    @GerarddeJong We close questions as duplicates if answers to an existing question answer a new question as well. In the actual case the answer on the linked question explains under which conditions an iMac can be used as secondary display for a MacBook Pro and what kind of cable is required. So at least from the information we currently have this looks like a duplicate to the "Do I need to use Thunderbolt" question in the post above. – nohillside Aug 26 '20 at 14:40
  • Having said that: From looking at the comments below the answer here it seems that the question is more about which type of cable is actually a TB cable. So if this information would be worked into the question (maybe even with a picture of the cable the OP is using) it might be a candidate for reopening (or a reason to update the answer on the older question with additional detail to help people pick the right cable). – nohillside Aug 26 '20 at 14:42
  • I don’t know anymore @nohillside. All I wanted to do is help Shannon get this working and make sure others can find the same question. While everyone has a right to an opinion, I feel bullied by Allan who seems to want to take the credit away from me, suppress my answer by marking it a duplicate (referring users to his own answer) and taking issue with everything I advise. This is only the second question I answer on the platform and now I no longer feel welcome as a contributor here. – Gerard de Jong Aug 26 '20 at 16:55
  • @GerarddeJong Closing a question as a duplicate means that there exist other questions where the answer also answer the question asked here. It is not directed against any answer given here and doesn't hide/invalidate them. They remain visible, they show up in search, may still be useful to future visitors, may get upvotes etc. Your previous answers have been well-received, please don't let a disagreement about the post here hinder you from participating further. – nohillside Aug 26 '20 at 17:35

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enter image description here Don’t use a cable like the one shown above! These do not contain the required licensed Thunderbolt chips (inside the connectors) to support Thunderbolt protocol. While they will work for a connection to a DisplayPort only monitor input, they will not support a Thunderbolt Display or iMac in Target Display Mode.

You need a cable that looks like the one below that shows a Thunderbolt Logo on each connector indicating it’s compatibility. I recommend the 2m cable, the 0.5 is too short unless you are comfortable leaving your MacBook closed under your iMac.

enter image description here If your MacBook Pro only has USB type C ports you’ll need to check which of those ports support Thunderbolt 3 and use Thunderbolt 3 to Thunderbolt 2 converter from Apple with a Thunderbolt 2 male-to-male cable to connect it to your iMac.

Here's an picture of the Thunderbolt 2 converter from Apple that'll do the trick.

enter image description here

Also check your MacBook's specs, and be sure to use the Thunderbolt ports, some are only USB C and it can be hard to tell.

Gerard de Jong
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  • I did some research and I what I read was that all ports on the Macbook Pro are Thunderbolt 3. I purchased a "USB C to Mini DisplayPort Cable, QCEs Type C to Mini DP Adapter 4K 6.6Ft Cord Thunderbolt 3 Compatible with MacBook Pro 2018 iPad Pro iMac 2019". I've tried every port on both the MacBook and the two on the iMac. Any idea what I'm doing wrong? – Shannon Poulos Aug 21 '20 at 21:57
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    Thunderbolt and USB-C are different communication standards but they use the same port/connector on your MacBook. The USB C to Mini DisplayPort Cable that you've purchased with convert USB C to Display Port which unfortunately is not going to work as your iMac requires Thunderbolt (not Displayport) for Target Display mode to work. What you actually need is Thunderbolt 3 to Thunderbolt 2. I'll add a picture to my original answer. – Gerard de Jong Aug 22 '20 at 17:29
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    @GerarddJong is correct, you need the Apple USB-C Thunderbolt 2/3 adapter and a Thunderbolt 2 cable from the 2012 iMac to the adapter to the MacBook Pro. – James Brickley Aug 22 '20 at 19:37
  • I bought a cable that I thought was Thunderbolt 3 to Thunderbolt 2. But it's not working. I'll add a photo. – Shannon Poulos Aug 24 '20 at 17:49
  • @ShannonPoulos please post the photo and let’s see. I assume you’re using original Apple branded adapters and an original Apple Thunderbolt cable. Let’s see. – Gerard de Jong Aug 24 '20 at 17:58
  • @GerarddeJong Photo posted above...not Apple brand.... – Shannon Poulos Aug 25 '20 at 18:57
  • Thanks @ShannonPoulos, I’ve only ever been able to get such things working with original Apple branded cables and adapters. These work because apple uses licensed Thunderbolt chips inside each connector. The cable you’ve posted a picture of is surely a USB-C to DisplayPort cable and does not have these features (which is why it’s comparatively inexpensive). What matters this the protocol these cables and adapter can communicate along and not the connectors, Thunderbolt the protocol you want to be supporting here. I’m sorry it’s expensive but old the original Apple cables and adapters work. – Gerard de Jong Aug 25 '20 at 19:35
  • @GerarddeJong I really appreciate your help. I don't mind spending the $ if it actually makes a different and it works. Thanks again. – Shannon Poulos Aug 25 '20 at 19:49
  • Those photos and statements about cables is not correct. There are several models of iMac that will work with DisplayPort and any quality USB-C cable is also a Thunderbolt cable. – Allan Aug 26 '20 at 08:18
  • Thanks @Allan. Kindly indicate which statements regarding cables is not correct and I will and I correct them. Also please also share the models of compatible cables you've found. Perhaps you can add your own answer to this question for others to find useful. – Gerard de Jong Aug 26 '20 at 15:39
  • I addressed it in the comment. Also, I've already written an answer; it's the dupe link. Also this is incorrect: Thunderbolt and USB-C are different communication standards Thunderbolt is is a technology. USB-C is a physical port type. I'm bringing this up because the wording is introducing confusion as to what's needed and what's not. – Allan Aug 26 '20 at 16:12
  • @Allan Maybe it would help if you (or Gerard) extend your answer to the original question to clarify misconceptions people may have about TB, USB-C etc and to make it easer for people to find the right cables. – nohillside Aug 26 '20 at 17:37
  • I'm trying to figure out how to do that @nohillside while keeping it constrained to the question. I commented here because Gerard was on the right track, but his answer should have been "you bought the wrong cable, you need a TB3 to TB2 adapter and a TB cable and not a DP cable." The top photo and the info on licensing and the chip and the info on USB-C versus TB is how we got here. – Allan Aug 26 '20 at 17:48
  • I've already addressed cables in many posts: https://apple.stackexchange.com/a/394518/119271, https://apple.stackexchange.com/a/306615/119271, https://apple.stackexchange.com/a/344119/119271, and as for USB-C versus TB, https://apple.stackexchange.com/a/288805/119271 – Allan Aug 26 '20 at 18:00