Target display mode on 2010 iMac 27"

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Target display mode on 2010 iMac 27"

Hi there. I've read all the posts about "target display mode" to utilize an old iMac as an external monitor. I am still having problems...

I have a mid-2010 iMac 27" that I would like to use as an external monitor for my 2015 MacBook Pro 13". These should be compatible based on this article (https://support.apple.com/en-us/HT204592). I have them connected with an Apple thunderbolt cable. Nothing happens when I hit cmd-F2 on the iMac. I am using the Apple wireless keyboard that came with the iMac.

could it be that I am using a wireless keyboard and not a wired KB?
should I be using a mini display port cable instead of a TB cable?

thanks!

Sean

iMac 27", macOS 10.13

Posted on May 15, 2020 12:26 PM

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Answer 1

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den.thed

Level 10

82,564 points

May 15, 2020 12:47 PM in response to SeanH1234

Yes the 2010 27" requires a Mini DisplayPort to Mini DisplayPort cable instead of a TB cable.

also see > Use your iMac as a display - Apple Support

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Answer 2

SeanH1234 Author

Level 1

9 points

May 30, 2020 6:09 PM in response to den.thed

Update: the Mini DisplayPort cable worked great. Thank you. In fact, I don't even have to press CMD-F2 -- when I connect the mini DP cable, the iMac 27" automatically goes into target display mode. Sound playing through to iMac also, which is nice. Still a couple issues:

the 27" iMac runs really hot. From searching and googling, it seems that this is not uncommon. But it is HOT. Like, really hot, hotter and fans louder than I've ever noted in 10 years. It concerns me. Thoughts?
I can't figure out how to adjust the brightness on the iMac. FWIW, I only have 1 keyboard (wireless) that is connected to the MBP 13"; there is a Magic Mouse connected to iMac however.
MBP running hot too in closed clamshell mode, but placing it vertical seems to help.

Thank you!

Sean

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Answer 3

May 30, 2020 8:38 PM in response to SeanH1234

SeanH1234 wrote:

... iMac runs really1. hot.... I can't figure out how to adjust the brightness on the iMac. ...

this might be a sign that the hard drive is about to fail. Not sure if you want to invest in upgrading the internal, I put an SSD in one of those and it runs cool and totally silent. You might think about getting an external to make a backup while you still can.

The F1 and F2 keys usually change brightness up and down, you can also go into System Preferences.

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Answer 4

den.thed

Level 10

82,564 points

May 30, 2020 7:40 PM in response to SeanH1234

You’re welcome.

When was the last time the iMac was cleaned and serviced?

If it’s been awhile or never, then you may need to shut it off and disconnect the cord. Then seriously vacuum out the bottom intake grill work, then blow out the upper exhaust vent slots and small exhaust vent behind the stand.

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Answer 5

BDAqua

Level 10

245,477 points

May 30, 2020 8:10 PM in response to SeanH1234

Have you blown the dust out of the intakes lately?

What temperatures does this App report? Especially the GPU.

This App can be used to speed up the fans, all my iMacs would be dead without it.

Never ever ever drop fan speeds below the speed that the Mac itself is calling for.

MacFansControl…

https://www.crystalidea.com/macs-fan-control

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Answer 6

SeanH1234 Author

Level 1

9 points

Jun 26, 2020 12:12 PM in response to Glen Doggett

Update: I figured out why my 2010 27" iMac runs so hot in target display mode and not in 'regular' mode: each time I go into TDM, the iMac brightness switches to the highest brightness. Every time. As long as I turn the brightness on the iMac back to normal range, it runs fine. I am posting this update since quite a few out there had the same apparent issue when I Googled it...

Last question: I have a new 2020 MBP 13" (4 ports) on the way😁. Can I use the same Mini DisplayPort cable to connect this new MBP to my 2010 iMac for TDM? I assume I'll just need an adapter to go from the new MBP TB3 port to the MDP male cable? Thanks!

Sean

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