Q: El Capitan unstable when connecting to external monitor using DisplayPort

Good morning,

I have been fighting this same problem for weeks now.  One HDMI (4K) display, and one Displayport to DVI.  When trying to wake from sleep, Mac is crashed and hard reset required to bring back again.  I think this is pretty much what everyone on this thread is reporting.

One thing I have found that makes this slightly better is to stop the mac from sleeping.  Not energy efficient I know, but no crash first thing in the morning.

Not a solution, but a short term workaround.

Sean...

What I have been doing lately, which so far has not resulted in the scrambled lock-up, is to wake the monitor before waking the Macbook.

I have a KVM switching between my Macbook and another PC, so what I've been doing is to have a working video session with the PC, then switch the KVM to use the Macbook, then immediately start repeatedly pressing on the keyboard to wake the Macbook before the monitor goes to sleep (which it will do within a few seconds if it doesn't receive a video signal).

I think the same thing might be possible without a KVM if you instead power off the monitor, then power it back on and immediately try to wake the Macbook (by pressing the keyboard) before the monitor goes into sleep mode.

I can't find any way on my Dell monitor to shut off the auto-sleep mode; maybe others of you have monitors that have an option to disable the monitor's sleep completely to see if that prevents the issue.

I have been experiencing an issue possibly related to this one. I have a Late 2015 iMac 5K with a 27-inch LED Cinema Display connected via the miniDP/Thunderbolt port. The iMac came shipped with OS X 10.11 GM and was then upgraded to 10.11.1.

When I wake the iMac from sleep, often the secondary display (the LED Cinema Display) is completely black. The system still sees it as connected (confirmed in System Information), and I can move and assign apps to it. However, I cannot see anything except on the primary display (the iMac).

When it gets into this state, only a reboot resolves it. (I have not tried disconnecting and reconnecting the cable.) Also, when this occurs, shutdown and restart (via the Apple menu or command-line) usually hang, and a hard reset is required.

NVRAM and SMC resets have had no effect.

I have noticed that the issue more frequently occurs when the iMac is awoken while a user is logged out. It does sometimes occur after wake while a user is logged in, but it seems the number of occurrences is fewer.

I logged an issue via Bug Reporter.

This LED Cinema Display was previously connected to my 2012 Retina MBP. I did not experience any issues with that system, which also ran OS X 10.11.x with this display.

My workaround continues to hold up. I always rapidly tap on the keyboard before and while turning on the monitor to wake the mac up without the monitor going into power save mode.

I still hope Apple got the message from our tickets. I never got a response from them, and this was NOT a problem before El Capitan, so something definitely got broken in that update.

Hello,

Short version: I'm experiencing similar problems as reported in this post, with the addition of some booting issues. Any solutions yet?

Long version: For months I've been happily using my 15" MBP 8,2 (early 2011) in dual display mode with an HP LP2465 monitor (1920 X 1200, 60Hz), connecting via a Mini DisplayPort to DVI Adapter plugged into the Thunderbolt port. Last week, I had the first of many crashes using this set-up. Both displays switched to an off-center image, and I was unable to access the menu bar. I hard restarted without the external display connected and used it like that for a while with no problems.

Since then, I've been occasionally trying to reconnect the external - it runs ok for a while, but soons freezes, usually showing a blue screen with horizontal stripes. The computer usually restarts itself when this happens, after a quick bout of fan whirring. Unfortunately, it has a lot of difficulty rebooting, even into recovery mode (safe mode and single-user mode both fail completely). It often gets hung up on the gray screen, either before or after login (which mysteriously has no "Guest" option anymore), and sometimes it just restarts itself halfway through the process. I've repaired the main drive, reinstalled OS X, reset NVRAM and SMC, and the problem persists. The only way to maintain stability is to forego dual display mode.

I ran Apple Hardware Test with the extended option, but found no problems there. Today I tried plugging in the MDP to DVI adapter without the DVI cable attached, and it soon crashed again, so the problem doesn't seem to be related to the dual display mode itself. I've also tried plugging in an MDP to VGA adapter, again with nothing external attached. So far, the system has remained stable (although it's been less than hour, so I'm not completely convinced). My next move will be to buy a new MDP to DVI adapter and see how that goes, but I sort of suspect it won't solve the issue. Why would a fritzy adapter cause a system crash? Any ideas?

Andrew

Sounds to me that there may be a hardware problem (video card or Intel video) in the MBP, despite the Apple Hardware Test not showing anything. Obviously, you're out of warranty by now, but maybe you have to take it to an Apple Store if there's one around you or send it in to Apple for repair. Better yet, get a newer MBP, even used, say, from OWC. (owc  dot  com)

I think you're probably right, and replacing it is going to be the ultimate solution. It's a huge shame because before this issue it was functioning beautifully. I will probably try the Apple Store first. Thanks for the quick feedback.

Just to follow up 10.11.3 has resolved this issue for me (knock on wood).

Hi Guys,

I belive I found the root cause of the problem and the solution as well. Just as you, I noticed that after updating to El Capitan my external monitor stopped working and the computer sometimes rebooted. I'm my case the problem started to show itself in the last update from Yosemite.

I found that the problem was that El Capitan has problems working with older Mini-display port cables (i.e. DP 1v). It was just a matter of replacing with a newer 1.2 DP cable that everything started working again like a charm.

I hope it helps!

Raoni

That’s not easy to do with the Apple LED Cinema Display.

I have had not any issues since updating to 10.11.3.

Yes, it is possible that Apple has solved its compatibility problem with older cables first in its own hardware. I tested my "solution" in a LG and a Philips 29'' monitor and the situation was the same: old cable not working, new cable OK. (while it worked in a older Mac with both cables in both monitors).

Issue is back with 10.11.4, in clamshell mode it gets the distorted screen and beach ball when you wake it up occasionally. Really annoying, getting ready to sell the computer because I don't have the time to "work through this issue" with applecare.

I am having problems too and my 4K display (LG 27MU67) looks just like the previous post... identical scrambling.  I'm using the cable that came with the monitor, Mini-DP to DP. 

I also ran Apple Diagnostics with the monitor connected, and got the error VFD002:  "There may be an issue with your display."     When the monitor is not connected, Apple Diagnostics checks out OK with no errors.