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Brand new Mac Studio, 2 identical brand new Samsung monitors connected via USB-C. Every log in is an adventure with the screen assignments. My $2,000 machine cannot remember where I designate each screen. What's up with that?
I'm having the same problem on a new Mac Studio with two identical Samsung monitors connected via Thunderbolt to DisplayPort cables. They look lovely and run at 144Hz, but switch sides randomly on every wake from sleep. I tracked down how to extract the EDID info, and it's very simple in a terminal:
ioreg -l | grep EDID
For me this shows my two monitors:
| | | | "DisplayAttributes" = {"SupportsSuspend"=No,"MaximumRefreshRate"=144,"SupportsActiveOff"=No,"PortID"=32,"ProductAttributes"={"ManufacturerID"="SAM","YearOfManufacture"=2018,"SerialNumber"=810889805,"ProductName"="C27JG5x","AlphanumericSerialNumber"="HTOKC02346","LegacyManufacturerID"=19501,"ProductID"=3928,"WeekOfManufacture"=51},"MaxVerticalImageSize"=34,"MaxHorizontalImageSize"=60,"HasHDMILegacyEDID"=No,"Chromaticity"={"Red"={"X"=44352,"Y"=20736},"Green"={"X"=18048,"Y"=43328},"Blue"={"X"=9984,"Y"=4032}},"DefaultColorSpaceIsSRGB"=No,"NativeFormatHorizontalPixels"=2560,"DefaultWhitePoint"={"X"=20544,"Y"=21568,"Gamma"=144179},"SupportsVariableRefreshRate"=No,"AspectRatio"=15,"MinimumRefreshRate"=50,"WhitePoints"=({"X"=20544,"Y"=21568,"Gamma"=144179}),"PreciseAspectRatio"=115652,"ContinuousFrequencySupport"="None","SupportsStandby"=Yes,"NativeFormatVerticalPixels"=1440}
| | | | "EDID UUID" = "4C2D580F-0000-0000-331C-0104A53C2278"
| | | | "DisplayAttributes" = {"SupportsSuspend"=No,"MaximumRefreshRate"=144,"SupportsActiveOff"=No,"PortID"=48,"ProductAttributes"={"ManufacturerID"="SAM","YearOfManufacture"=2018,"SerialNumber"=810889805,"ProductName"="C27JG5x","AlphanumericSerialNumber"="HTOKC02337","LegacyManufacturerID"=19501,"ProductID"=3928,"WeekOfManufacture"=51},"MaxVerticalImageSize"=34,"MaxHorizontalImageSize"=60,"HasHDMILegacyEDID"=No,"Chromaticity"={"Red"={"X"=44352,"Y"=20736},"Green"={"X"=18048,"Y"=43328},"Blue"={"X"=9984,"Y"=4032}},"DefaultColorSpaceIsSRGB"=No,"NativeFormatHorizontalPixels"=2560,"DefaultWhitePoint"={"X"=20544,"Y"=21568,"Gamma"=144179},"SupportsVariableRefreshRate"=No,"AspectRatio"=15,"MinimumRefreshRate"=50,"WhitePoints"=({"X"=20544,"Y"=21568,"Gamma"=144179}),"PreciseAspectRatio"=115652,"ContinuousFrequencySupport"="None","SupportsStandby"=Yes,"NativeFormatVerticalPixels"=1440}
| | | | "EDID UUID" = "4C2D580F-0000-0000-331C-0104A53C2278"
and you can see that the two monitors produce absolutely identical output – same serial number, same UUID. Samsung needs a slap, or we need a way to anchor monitor ID to physical port – but the port ID is right there in the output, so macOS could tell them apart anyway! So while Samsung shouldn't use duplicate serials, macOS could work around this. Searching for this 810889805 serial number finds several people who apparently have the same one as I do.
I previously had these same monitors connected to a Mac Pro with an RX580, both connected via HDMI, and while they had other issues, they didn't switch sides.
I use two Dell 4k 32 inch display connected most anyway I want without issues. Years ago I gave up on Samsung displays.
Do you have these monitors daisy chained or plugged into two separate ports. Daisy chaining does not wrk.
Not daisy chained
as I said above:
a) get Samsung to put the display serial number in the correct field in the EDID message sent to the Mac -OR-
b) don't use twin displays that have this issue.
Please let us know your results, as this appears to be, "controversial".'
Create two new Display Profiles using the same base profile. Name one Samsung(1) and the other Samsung(2). Then setup each display using a different display profile to distinguish one from the other.
I feel like Apple’s software should be able to identify displays simply by which port they are connected to…
Of course being APPLE there will always be those on here who will try to convince you that it's not their problem. Don't buy it..
OMG..
Doesn't even deserve a reply.
Displays that do not provide the serial number in the correct EDID field are DEFECTIVE.
All other displays are presumed to be NOT DEFECTIVE, so the list is 'any other display'.
Great stuff, thanks for persevering!
T-A-Gill, I greatly appreciate the leg work you have done in trying to figure this out. It is good to know Apple is aware of this thread and the issue it refers to. Mahalo! From Michigan.
Many thanks for your efforts.
God Save The Queen!
From Hampshire, England
This is a big deal for us and our developers. Hoping for a fix soon.
How do I make my Studio remember which monitor is which?
