Able to Network Share Screen but displays do not detect

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Able to Network Share Screen but displays do not detect

Mac Pro 6,1

I’ve attached my display and keyboard/mouse. I hold option to get the boot-loader, I choose Macintosh HD, I Boot MacOS but the display turns off about 25% the way through boot every time.

I connect a network cable and I can then Share Screen. Windows 10 does boot ( I have bootcamp installed).

Back to network Screen Share now, I can use Disk Utility: verification shows no errors S.M.A.R.T status is verified.

Display preferences just says “unknown display “. I have tested all the Display ports and HDMI. can verify they work under windows. MAC OS won’t detect the displays the same way when they are connected.

So what can I do to get MACOS to detect the displays again as per normal?

Ive reset the NVRAM, tried to boot MAC OS in Safe Mode. Internet recovery and booting from USB MACOS image is not helpful since the displays also cut off about 25% of the way through booting.

My recovery partition has a kernel Panic when I choose to boot from that I can’t use that. I can set the computer to target disk mode if I want so I used Disk Utility to verify the disk & permissions. Image: The MacPro6,1’s SSD checked out fine(target disk mode).

About this Mac also shows the two D700 displays coming up in the Hardware list and there are 3 thunderbolt devices listed (0,1,2), but displays are not listed as attached under the Thunderbolt.

Mac Pro, OS X 10.10

Posted on Oct 27, 2020 3:12 PM

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Answer 1

olaf261 Author

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5 points

Oct 28, 2020 5:54 PM in response to Grant Bennet-Alder

Hi Grant.

I am aware of the EDID. I mention windows only because it proves that there hardware works, so it must be a MACOS software problem.

So for the Mac to detect my ASUS display on VGA and not on DVI, am I right in saying that EDID handshaking is working on VGA but not on DVI or HDMI? ( I’m using proprietary MAC mini display port adaptors for this.

I’ve started a new topic for this. https://discussions.apple.com/thread/251969611

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Answer 2

olaf261 Author

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Oct 28, 2020 2:44 PM in response to olaf261

Oh boy, so VGA works. My Display has DVI-D and VGA Input.

It’s only DVI and HDMI that does not detect displays on MACOS, Windows detects DVI VGA HDMI displays fine. So how can this be fixed on the MACOS side?

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Answer 3

Oct 28, 2020 2:54 PM in response to olaf261

olaf261 wrote:

...

It’s only DVI and HDMI that does not detect displays on MACOS, Windows detects DVI VGA HDMI displays fine. So how can this be fixed on the MACOS side?

Windows does not DETECT any displays. You simply tell it what resolution you want, and it sends out that data stream.

MacOS is FAR more complex:

to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display.

This query is only sent at certain times:

• at startup

• at wake from sleep

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences (from another display)

This query and response Is sent over the EDID wires in the interface.

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Answer 4

olaf261 Author

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5 points

Oct 27, 2020 5:15 PM in response to olaf261

Some further information: Verbose mode on startup shows this text before the screen cuts out. Thereafter the session can only be resumed using Network Screen Share.

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Answer 5

olaf261 Author

Level 1

5 points

Oct 27, 2020 5:21 PM in response to olaf261

The detect displays button, system preferences: (hold option) does not work either

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Able to Network Share Screen but displays do not detect

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