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h_correia Author

Level 1

8 points

Messed up External Display After Security Update

Hello all,

This morning, my Mac wasn't recognizing my external display. I tried a different HDMI port, different cable and even a different display. I decided to restart the Mac, which I don't do too often, and saw there was a security update ready, so I went on with the update. After the update was completed, the overscan on the external display was messed up and I couldn't see the status bar at the top and the screen looked much more pixelated. I'd had this issue with the other external display, but never before with this one, it just worked. Since I'd had the issue before and, for god knows what reason, there is no easy option to change the overscan on the Displays menu, I went to /var/db/.com.apple.iokit.graphics and changed the underscan value. I could get the size to fit, but the display still is much more pixelated than before, as if the Mac weren't using the full 1080p. I don't have a recent Time Machine backup, so that is not an option. Does anyone have any tips on how to go back to the old, default, "just works" setting? I'm on 10.14.6 on a 13' MBP, Early 2015. Thanks for any help!

MacBook Pro 13″, macOS 10.14

Posted on Oct 26, 2020 8:17 AM

Top-ranking reply

h_correia Author

Level 1

8 points

Posted on Oct 26, 2020 8:28 AM

As it turns out, there was a pretty easy fix, and the problem had nothing to do with the security update. My external display (a Samsung TV) has two HDMI ports, HDMI1/DVI and HDMI2. Before the update, I had switched ports to HDMI2 to try and troubleshoot and when the Mac restarted, it recognized the display again, but with this weird setting. After I switched back to the HDMI1/DVI port, the pixelation was gone and it was actually underscanned, so I went back to the original value in iokit.graphics, restarted and everything was back to normal. I guess it's something with the TV side then, not really sure why it interprets the signal coming from the two different ports differently. I'll leave the post up here anyways, in case someone in the future has a similar issue.

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Messed up External Display After Security Update

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