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I purchased two new monitors recently and both had pretty bad overscan (underscan? there were black bars around the screen). My mac no longer has the setting it used to have in the Displays section of System Preferences to fix this.

I have answered my own question but I am interested in a solution that doesn't require a restart.

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1 Answer 1

Reset to default
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/var/db/.com.apple.iokit.graphics is the configuration file for displays on macos. The entries are not at all labeled, but in my experience a new monitor will be on the bottom of the list. Each entry is structured as follows:


    <key>IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/IGPU@2/AppleIntelFramebuffer@2/display0/AppleDisplay-6b3-27ae</key>
    <dict>
        <key>cyuv</key>
        <integer>268435456</integer>
        <key>pscn</key>
        <integer>10000</integer>
        <key>startup-timing</key>
        <data>
        AAAAAAAAAIAJMACAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
        AAAAgP4hCgAAAACA/iEKAAAAAID+IQoAAAAAgAcAAGoAAAAIAAAAIAAAADgE
        AAAnAAAAGQAAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAAAAAAAAAAA
        AAIAAAAAAAAAAgACAIAAAQAAAAAAAAAAAAAAAAAAAAAA
        </data>
        <key>version</key>
        <integer>2</integer>
    </dict>

The pcsn key and following integer are overscan. My first monitor had some value besides 10000, and changing the value to 10000 fixed it. I tried this with my second monitor and it didn't work, so I just deleted the last few entries. Either method requires a restart.

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  • After updating all pscn values less than 10000 to 10000, it did the trick for me. Thanks
    – Long Nguyen
    Commented Oct 18, 2023 at 3:18

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