Sleep/wake issues with Mac Pro, GTX 680, LG 34UM95-P

[savoirfaire]

Hey, folks. I'm wondering if someone might be able to help me out here. I am using a flashed Mac Pro with a GTX 680 2gb Mac Edition (with Yosemite). I had been using a pair of Dell S2240Ms connected via DVI with no issues but switched to an LG 34UM95-P ultrawide (3440x1440) I bought over the holidays. It is connected via DP because HDMI only supports 3840x2160 at 30Hz or 4096x2160 at 24Hz whereas DP supports 4096x2160 at 60Hz. However, since switching displays, I've found that when the Mac Pro wakes from sleep, it often shows just the pointer arrow against a black screen. The arrow seems to respond to items that are on the invisible desktop, switching between arrow and cursor as a I drag the mouse around. The only way I can get it to display the desktop again is by unplugging the DP cable and plugging it in again. There have also been 2 or 3 moments where the screen flickers/goes black for a split second while I am using it. Any idea what the issue might be?

 

[ActionableMango]

Seems to be a common problem with Macs and LG 34UM95-P.

https://forums.macrumors.com/threads/mid-2012-mp-and-lg-34um95-wake-from-sleep-problem.1947647/
https://forums.macrumors.com/threads/lg-34um95-display-boot-issue.1797744/

I saw more complaints over in the Massdrop forum too.

 

[savoirfaire]

Thanks for taking the time to respond, Mango. I think I sorted it out this morning. I tried reversing the direction of the DP cable since someone on Apple's discussion forums said that worked for them, but it didn't work. Then, I did what I should have done in the first place which is install Nvidia's web driver instead of using the OS X default graphics driver. That seemed to work, so then I upgraded to El Capitan and installed that version of NVidia's web driver and ran into a different problem. I couldn't wake up the computer from my Logitech USB mouse/keyboard anymore, but if I plugged a flash drive into the front ports it would wake up and the screen would wake up appropriately. Tried putting it to sleep again and then plugging the flash drive into my USB hub. Nothing. At that point, I remembered that my Logitech Unifying Receiver was plugged into a hub, so I moved that to one of the built-in rear ports, and now USB mouse and keyboard wake up the Mac Pro fine and the display wakes up properly. Not sure why waking up from USB hubs worked in Mavericks and Yosemite but not in El Capitan. Seems like every new version of the OS has its own quirks to sort out.