MP 1,1-5,1 Radeon VII don't like 30" ACD on Mac Pro 5.1

[ak-78]

Hi all, I have working Mac Pro 5.1 with 30" Apple Cinema Display and Sapphire RX 580 running Monterey with Latest OCLP.
Everything work as it should with a boot screen as well.
Recently I've got Sapphire Radeon VII, did Pixlas Mod.
When I drop Radeon VII into Mac Pro I'm getting normal boot screen and progress bar,
only after Mac OS boots I'm starting to get weird screen behaviour.
Monitor starts intermittently blinking, I mean for a several seconds I'm getting desktop on the screen,
then suddenly screen turns off, then back to desktop again and keeps shutting off and on.

Checked RX 580 on Mac Pro with 30" ACD, all works well.
Checked Radeon VII on a PC under Windows with 30" ACD and star.tech adapter and all working well.
Put the card back in to Mac Pro with 30" ACD same blinking behaviour.
Plug 23" ACD into Radeon VII on Mac Pro and all working well.
Than I though maybe it's Pixlas mod I did, double checked all the cables and they intact.
I even plug different PSU into the card with 30" ACD same weird on and off thing happening.
The card works in Mac Pro with 23" display , but not with 30".
Same star.tech adapter was used in both cards.
Honestly, don't know what else I should try.

 

[reader50]

Reminder - you've switched graphics cards. Reinstall OCLP with the Radeon VII installed. Then redo root patches to account for the revised drivers. OCLP will only fix up drivers for a card that's present.

If your VII is too unstable for this, you might need both GPUs installed, with monitor attached to the RX580. Once OCLP is all patched up, you could remove the 580 and put back any cards removed to make room.

 

[ak-78]

I've updated OCLP in the applications to latest version with Radeon VII in the Mac Pro ( it was blinking all this time) restarted, then run OCLP and re apply root patches. Do I have to rebuild it from scratch? It's weird that Radion VII works with 23" Cinema Display))

 

[reader50]

Sounds like you reinstalled the app in your Applications folder? That wasn't what I meant.

In the OCLP app window, click on "Build and Install OpenCore". It will update the OpenCore on your EFI partition, which is what boots first. Before macOS boots, to smooth over certain incompatibilities. Taking into account all cards that are present.

Reboot. Then open the OCLP app again, and redo the Post-Install Root Patches. Reboot again, and you should be good.

 

[ak-78]

reader50, Tthank you so much for clarification!!! I'm such a dumbass, I never rebuild OP just updated package and perform root patching. I'll try that tomorrow with the card in and get back here to let you know how it's went. Thanks again.

 

[ak-78]

Well I did "Build and Install OpenCore" then Post-Install Root Patches of course with the card in the computer and still getting same behaviour. 23" Apple Cinema Display working normally with Radeon VII . Although 30" works fine with RX 580 Nitro+ in the same machine. Mystery

 

[reader50]

In macOS, check your displays settings with the 30" plugged in. Settings -> Displays -> Advanced... (button) -> Show resolutions as list (slider) so you get actual numbers.

It should be 2560 x 1600 at 60Hz or less. If macOS defaulted to some oddball setting, the display might well flicker as it loses and regains sync. Try some lower settings manually, including 30Hz. See if the flickering goes away.

You can also try a different brand of adapter. I've occasionally seen issues where a monitor liked one adapter, but not another.

 

[ak-78]

Hi reade50. Thank you for your help, I appreciate it.
In Mac OS Monterey there is no advance option for display resolution and no setting for frequency, only "show all resolutions", I tried different ones to no avail. I also log in to Mojave , same on and off behaviour.
Just ordered EVGA PowerLink and going to buy 3dClub adapter.
Really starting to think about fresh Mac OS manual install OC on different nvme ssd.
Mean while I'm using 23" ACD, cause I'm tired of switching cards back and fourth.

 

[reader50]

If memory serves, in Monterey the option is in the main Displays window. "Show resolutions as lists" or something similar. Or maybe hidden behind an Options button.

Bonus - with multiple adapters, you can have both monitors plugged in at the same time for easier testing. I personally like dual displays.

Another place you can get your display output settings, possibly including the refresh Hz: Apple menu (hold Option key) -> System Information -> Graphics/Displays.

Under the graphics card, it should show the connected display, with all current settings.