I got through literally all posts you made in last days. I'm sitting here with the same issue although my machine is MacBook Pro 13 2011. I even downloaded clover and clover configurator but I'm completely unaware what should I do with it in my case. And I don't want to break anything.
I got that you don't have that much time to mess around (jobs and everything) with helping but I would highly thank you if you could somehow put an instruction on what to do to make my display port working the same way you did. I don't mind waiting at all. Thanks anyway for putting any info on the common issue with DisplayPort me and others are experiencing...
Fair enough.
Here is the short version that might give you results:
0. It helps to install an OS on the drive you intend to use Clover on. (more on this in a sec).
1. Using Clover Configurator, use it to mount an EFI Partition, preferably one that is on a USB Drive so you won't mess up your system. I recommend a 32 GB or bigger USB Drive for this and it seems to help to have an OS installed on this disk for the EFI Partition to show up. [Also Clover Configurator tends to hang up a lot, so do not be alarmed if you have to force quit it and reopen it].
2. Then using Clover install clover on the mounted EFI partition. Use all the default settings.
3. Reboot holding down the option key.
4. On most systems you will have 2 EFI Partitions for the disk that you installed Clover onto. The Clover EFI Boot Loader is always directly next to the OS. And using an External USB Drive makes this really obvious. The other EFI Partition is for the system. It will be on the far left. Clover in the middle right next to the OS on the USB Drive.
5. select that EFI partition and Clover Boot Loader should appear.
6. Select the Disk you want to keep using the cursor keys on the Clover Boot loader.
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Bonus:
If your system happens to not boot, change less stuff by creating a new config.plist file. In the SMBIOS section on Clover Configurator, use the upload / down arrows in the lower right corner, pick the iMac 10,1 27" 2009 iMac config. Copy its Board ID. It is short Mac-XXXXXX. Then select the config to your computer system instead, and just past the board ID. This is the least evasive approach. And keeps most of your SMBIOS Settings to standard.
Mount the EFI Partition again and replace out the config.plist file
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I am traveling and did all this from memory. I hope if helps you out. Let me know if you have any questions. I'll be happy to elaborate.
I do not condone this method and fully intend to create a better option that does not rely on a boot loader. I've dealt with Clover last year when we were getting black screens and KP's ln Mac Pro 3,1 before the Telemtry culprit was discovered.
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If all ends well, you will have hopefully DisplayPort or MiniDisplayPort working again.
Be patient and try to use a USB Drive if you have one. That way you can reformat it as much as you want. You can use an internal disk, but until you've mastered this technique, I don't recommend trying it.
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BONUS 2 how to mount your own EFI Partition:
You can mount EFI partitions manually using the Command line. It takes a little longer but it does work.
See:
Here’s the answer to another reader request… According to WIkipedia, “On Apple–Intel architecture Macintosh computers, the EFI partition is initially blank and not used for bootin…
themacadmin.com
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Please note the admins of this site do not recommend using clover. I have supplied this info as requested. It is meant to be a temporary workaround only. Do not attempt installing Updates using Apple's Software update. They will fail after a long while. Apple has added extra copy protection on the point updates.