NVRAM reset and monitor output screwed (black screen) [OCLP]

[Overplay5652]

There is a tons of posts about this problem everywhere, and I've found no solutions so far.

Here the story :

Because I had a "Waiting for debugger" message after installing Mac OS Big Sur on my Mac Mini mid 2011 with OCLP 2.2.0, I decided to flush the Nvram, as suggested by some.

I did it with command line first and also with Option CMD + P + R key, several times (hearing the chimes for more than 10x). All leaded to black screen and no boot option.. I've tried numerous things since then and nothing worked.

• Different keys combo ant start: option, option+R, option-cmd+R, etc.
• Resetting SMC
• Changing the monitor output to mini Display / HDMI
• Tried to put my old hard drive with the same OS (to see if something has been messed with EFI partition)

Obv, I tried different HDMI cables. Obv monitor and cables have been tested with another PC's and are working fine. I also tried mini display port, and another monitor. Nada!

And then, boom, I plugged the Mac Mini to my 1080p TV and now it worked! Ok..

So I've booted up in Mac os Sierra, rebooted fine. Still ok on my TV, but however, when I plug it back to my monitor, arwww... I still have a black screen!

Any idea how can I revert this?

 

[EliteMacx86]

There is a tons of posts about this problem everywhere, and I've found no solutions so far.

Here the story :

Because I had a "Waiting for debugger" message after installing Mac OS Big Sur on my Mac Mini mid 2011 with OCLP 2.2.0, I decided to flush the Nvram, as suggested by some.

I did it with command line first and also with Option CMD + P + R key, several times (hearing the chimes for more than 10x). All leaded to black screen and no boot option.. I've tried numerous things since then and nothing worked.

• Different keys combo ant start: option, option+R, option-cmd+R, etc.
• Resetting SMC
• Changing the monitor output to mini Display / HDMI
• Tried to put my old hard drive with the same OS (to see if something has been messed with EFI partition)

Obv, I tried different HDMI cables. Obv monitor and cables have been tested with another PC's and are working fine. I also tried mini display port, and another monitor. Nada!

And then, boom, I plugged the Mac Mini to my 1080p TV and now it worked! Ok..

So I've booted up in Mac os Sierra, rebooted fine. Still ok on my TV, but however, when I plug it back to my monitor, arwww... I still have a black screen!

Any idea how can I revert this?

Ensure that the OCLP chain is loading which means when you boot the Mac, it should straight go and boot via the OCLP drive and not the embedded one. Some monitors may require a certified cable to work. Try swapping the cable which works with your TV and then check.

 

[Overplay5652]

Hello @EliteMacx86 and thanks for your kind answer.

Ensure that the OCLP chain is loading which means when you boot the Mac, it should straight go and boot via the OCLP drive and not the embedded one.

How can I verify that?

some monitors may require a certified cable to work. Try swapping the cable which works with your TV and then check.

I did, same monitor that is working on the TV. Multiple others one. No screen.

 

[EliteMacx86]

How can I verify that?

Shut Down your Mac. Start and check if you can automatically boot to macOS via OC. If it boots, it means the OCLP is working as expected and there is probably some sort of bug in the NVRAM itself.

I did, same monitor that is working on the TV. Multiple others one. No screen.

It could be likely possible that the machine fails to output any display on a higher resolution than 1080p. Use an active certified cable and you should have the display on your other monitor/TV. If the other monitor/TV is also 1080p and using the same cable (where it works with the other monitor), check for the correct settings on your monitor.

Also, is your Mac mini only with Intel Graphics or the AMD?