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MacBook Air not filling entire screen on Dell U2415 External Monitor

I have an early 2015 MacBook Air, and the image is not filing the entire screen on a Dell U2415. I've tried mirroring the displays and selecting "Best for Dell U2415", resetting the NVRAM, rebooting, and running diagnostics on the monitor (all is fine—screen fills to the edge) and every combination of power cycling/sleeping both the MBA and the monitor. There is nothing in the the monitor's settings for underscanning or adjusting the vertical/horizontal size. I'm running it at its native resolution of 1920 x 1200


The same issue was reported here:

https://discussions.apple.com/thread/7945034


Two things about this are strange. In the above post, a user reported that it didn't work for them in whichever Sierra version they were running, but it did work in Yosemite. I'm running Yosemite. The other thing that kind of has my head spinning is that I would swear that it was working fine last night when I first hooked it up because I just bought it and was checking everything closely to ensure it was working. I would have noticed this.


The only difference is that, last night, I had the monitor turned upside down and rotated 180° in the Display Preferences because it clears the arm on my monitor mount more easily when upside-down. I turned it top-side-up because, for some weird reason, the text cursor displays about 1/4" above and to the right of where the actual insertion point is when monitors are rotated in Yosemite. (I had this issue with another monitor and though it was a problem with the monitor, but now I know that's not the case.) So, I tried setting the Rotation setting to 180° degrees again, and the problem still persists.


It doesn't appear that the OP of the above thread ever found a solution. If he did, he didn't post it. Does anyone have any idea what else I could try? Does anyone else remember the days before Jonny Ives took over OS development and Apple products "just worked" as advertised?

Posted on Aug 21, 2019 1:08 AM

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Posted on Aug 21, 2019 2:05 AM

Well, after reading the post on Dell's forums about the reinstall fixing the issue, I rebooted into safe mode and then restarted normally and the issue was resolved.


I'm glad I know I'm wasn't hallucinating when I had it working last night. Not that there is anything wrong with hallucinating. I just want it to happen when I've done something to make it happen, like hypnosis!

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Aug 21, 2019 2:05 AM in response to Glen Schuler

Well, after reading the post on Dell's forums about the reinstall fixing the issue, I rebooted into safe mode and then restarted normally and the issue was resolved.


I'm glad I know I'm wasn't hallucinating when I had it working last night. Not that there is anything wrong with hallucinating. I just want it to happen when I've done something to make it happen, like hypnosis!

Aug 21, 2019 1:56 AM in response to Glen Schuler

Someone was able to fix this issue with a clean install of Yosemite here:

https://www.dell.com/community/Monitors/U2715H-Macbook-Air-black-bars/m-p/4605708/highlight/false

However, this is not what I call a solution. I would take me weeks to do a clean install and reinstall the 700+ apps and audio plugins I need, not to mention all of the fine tuning, customization and automated tasks that I've spent years setting up. Neither is "upgrading" to Mojave. Mojave froze the first time I tried to use it. All I did was try to extract the .zip file for my UAD plugins and the whole system froze. Not just the Finder. The entire system. Eternally spinning beachball with no response to anything other than a hard restart.


There must be a cache or preference file that can be deleted or changed that will fix this if a clean install resolved the issue. Any ideas?

MacBook Air not filling entire screen on Dell U2415 External Monitor

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