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leo015 Author

Level 1

10 points

Can't achieve full resolution (2560x1440) on external monitor from iMac

Hello everyone,

I have a Late 2009 10,1 iMac (Core 2 Duo, Radeon HD 4760 256 MB, SSD installed, 8 GB Ram).

The issue at hand is that it does not push full resolution on my external monitor (Acer H277HU which is 2560 x 1440). It only pushes up to 1080p.

Initially I had thought that my cable was the problem however I just bought this one (https://www.belkin.com/us/cables/audio-video-cables/mini-displayport-to-hdmi-cable-4k/p/p-f2cd080/) which should solve the issue as it supports greater resolutions but unfortunately it has not.

Any ideas would be appreciated,

Thank you

Posted on Jul 15, 2021 4:47 AM

Top-ranking reply

den.thed

Level 10

83,038 points

Posted on Jul 15, 2021 6:15 AM

You're welcome.

Because the 2009 iMac's GPU and software does not support 2.5k HDMI.

It only understands older Mini DisplayPort Resolutions up to 2560 x 1600.

If holding the Alt (option) key and clicking on the Scaled button does not reveal resolutions above 1080p with that connection. Then you should be able to get up to 2560 x 1440 or 2560 x 1600 using a Mini DisplayPort to Display Port cable connected the that monitors Display Port input.

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Can't achieve full resolution (2560x1440) on external monitor from iMac

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