iMac 27" external display does not show all resolutions

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Tomlar1977 Author

Level 1

5 points

iMac 27" external display does not show all resolutions

Hi there!

Just bought a Samsung S27D850, which has a max resolution of 2560x1440. This is working just fine on my rMBP with the supplied HDMI cable.

I have an iMac 27" mid 2011 (3,4 GHz i7 with the 2 GB gfx card), which according to Apple specs should be able to run up to a 30" display in 2560x1600. When I connect the Samsung to the iMac, either via Thunderbolt -> DVI or Thunderbolt -> HDMI, all I can choose from on the Samsung is 1080p, 720p, 1600x900 and 1344x756? I searched a lot, and found various pages where people had similar problems with Dell 27" monitors, and some hacks to edit the EDID informations from the monitor, but this did not help 😟

Anyone having some ideas how to make my external display work correctly?

PS: Both machines are running 10.9.4, so it should not be an issue with OSX, and I know for sure that at least the Thunderbolt to HDMI adapter is qualified for this resolution, as it is 4K compatible (bought is because I thought it was the Thunderbolt -> DVI that was the issue)

Merry christmas!

/Tommy

iMac, OS X Mavericks (10.9.4)

Posted on Dec 23, 2014 10:26 PM

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Answer 1

Dec 24, 2014 6:07 AM in response to Tomlar1977

Go to System Preferences > Displays - Display.

Hold the Option button and select Scaled.

More resolutions should be now listed for selection. Does the resolution you want now appear?

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Answer 2

Tomlar1977 Author

Level 1

5 points

Dec 24, 2014 6:11 AM in response to actionmarker

Not to be rude, but if I don't select Scaled, I wouldn't even be able to see which I could choose from :=) So yes, been there, done that, even holding the Option while clicking Scaled, which gives some more resolutions, but all lower than 1080p :/

/Tommy

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Answer 3

Dec 24, 2014 7:16 AM in response to Tomlar1977

I didn't doubt that you had selected Scaled to see the available resolutions, however many users are not aware that when the Option button is held too, it will reveal more resolution options. As you had not stated that in your original post that you had tried it, I could not read your mind from here.

As you say, the iMac should be able to drive the resolution. Even though the cables work on the rMBP, its possible that this older Mac may only be able to achieve that resolution using direct Thunderbolt or DisplayPort to Dual-Link DVI. Looking at this page iMac (27-inch, Mid 2011) - Technical Specifications it does not explicitly say what connection type will achieve the resolution, but I do note, that it doesn't mention HDMI at all.

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Answer 4

107MP

Level 1

44 points

Dec 24, 2014 9:42 AM in response to Tomlar1977

I didn't understand that are you trying to connect this display by DVI. I think that you need to connect it in other way for example by DP or HDMI. I'm not sure but DVI does not work with 2K resolution. Try connecting it with only Thunderbolt to HDMI adapter.

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Answer 5

Tomlar1977 Author

Level 1

5 points

Dec 25, 2014 1:38 AM in response to 107MP

As I write, I tried both Thunderbolt to DVI, as Thunderbolt to HDMI - and the HDMI cable is compliant to the resolution, as my rMBP starts on 2560x1440 when I connect that one to the display - which also gives me the idea that it also can't be the EDID information, because then the rMBP would also not be able to see and use that resolution!

/Tommy

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Answer 6

Mar 25, 2015 9:09 AM in response to Tomlar1977

I'm having the same issue.

2 external monitors.

Acer 21" max of 1920x1080

Monoprice 27. max of 2560x1440

I can't get the Monoprice higher than 1920x1080

BUT-- I went back & looked @ the adapters I bought.

The TBolt to DVI adapters max rez is 1920x1080. States in clearly in the Specs

TeraGrand http://www.amazon.com/gp/product/B006FKRSUY/ref=oh_aui_detailpage_o07_s00?ie=UTF 8&psc=1

Cable Matters http://www.amazon.com/gp/product/B00ESM3JKY/ref=oh_aui_detailpage_o06_s00?ie=UTF 8&psc=1

So;

Look @ at your adapter's spec's

PS--

I haven't found an adapter that will do 2560 yet.

Lemme know if you find something

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Answer 7

pc_workx

Level 1

5 points

Apr 12, 2015 6:58 PM in response to mongo.imac

The samsung s27d850 has a display port, you may try Displayport to MiniDisplay port. I have the same set up with my iMac 2013, same samsung monitor, and was able to get 2560x1440 .

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