New 27" Thunderbolt Display Flickers when attached to new 27" iMac

I have MBPro 8.1 (early 2011) which I've upgraded recently to 16Gb

and Thunderbolt Display

It started flickering sometimes, same problem as described by many in this topic.

I've tried resetting NVRAM - doesn't help.

It seems the problem is somehow related to mac os memory management and tb video adaptor's memory manaagement.

Ruslan, I think you are right.
I'm not sure exactly, but it seems that display start flickering after memory upgrade ((

Hello all,

It's been only few days so I can't be 100% sure yet but after upgrading to Mavericks the flicker problem seems to be gone.

Anybody who used to have those flickers still having some with Mavericks ?

No... still happening for me... although it does seem less frequent.

Ok.... I may have had a breakthrough! I haven't had one flicker so far today, what I did differently is that I plugged in the thunderbolt cable and then rebooted the imac a couple of times (for unrealted reasons) but it seems that having the cable plugged in from the boot up.. that perhaps that makes a difference. I am crossing my fingers, because this issue drives me NUTS!

My flicker is still there. I upgraded my mac mini and my laptop (mac pro w/ retina) with Maverick. I get flickering, then scrambling, then shut off. Both my machines have 16 GB ram in them. Is there any way to connect the thunderbolt display other than the built in cable?

Try zapping the pram. It has cured the issue for me.

1. Shut down the computer.
2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Immediately press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.Continue holding the keys down until the computer restarts, and you hear the startup sound for the second time.
5. Release the keys.
6. Mended?

I too am experiencing this issue. I've got the 27 inch Thunderbolt display connected to a MPBR with 16gb ram. I am a web designer so I use Photoshop and other GPU / CPU intensive programs. After doing some extensive testing, I found a fix that works for me.

1) Download gfxCardStatus from here: http://gfx.io/

2) Open it up and click the mini icon in OSX top bar.

3) Select descrete only.

I think my MBPR and Thunderbolt display have an issue determining which source to use for the display feed. Its been 2 hours without any flickering now and this usually happened as soon as I connected my display.

Will provide a further update.

2012 13" cMBP, 8GB RAM. Two Thunderbolt displays and a G-RAID 4GB Thunderbolt drive at the end of the chain. Second display would flicker when the G-RAID had disk activity, either between folders on the drive or when copying to the drive. Intermittent and frustrating as it was difficult to track down. I was with Apple Tech Support where we did the following:

- switched display order

- create a new paritition for new install of Mavericks

- connected displays and G-RAID to MBA

In all cases, the flicker would show up on the second display. Had a bit of a breathrough when my 2nd display stopped recognizing the G-RAID. Verified the issue was with that display and have a service scheduled to replace the logic board and all-in-one cable. Fingers crossed this works and, perhaps at the same time, also takes care of the audio static decay that occurs...

I have a similar set up to you, late 2013 rMBP 15, i7, descrete Nvidia 16GB Ram, using it closed with two ATD's and have a Lacie 2Big 6TB Thunderbolt, depending on which monitor the drive is connected two causes the issue, so not sure a new display is going to fix the issue, but let me know, for now im going to plug it directly into the MBP and see if the displays stop doing it.

Personally I think its a power supply issue, when thunderbolt is active there is a lack of power so the screen shuts off briefly?

Zap the PRAM three times. It worked for me.

Update: Apple sent a tech out to replace the logic board and external tbolt cable/laptop power feed on ATD #2. It didn't fix the flickering screen. I tried different ways of connecting everything together, switching the order of connection between ATD #1 and #2.

Solution (partial): The flicker does not occur when the GRAID drive is the start of the chain. I still have the audio static/degradation during file transfers and we are in the process of troubleshooting that. For now, however, the screen flicker doesn't occur when the GRAID is the beginning of the Thunderbolt daisy chain.

I tried zapping the PRAM multiple times prior to this. It never worked in my situation.

Update: so after much troubleshooting over the phone and in-store, this is what was found in my situation...

We tried is with Mountain Lion and Mavericks. We tried it with an in-store cMBP 13 and rMBP 13 (Iris). We tried it with my GRAID 4TB, in-store GRAID 4TB and Lacie 6TB. Whenever the drive was first and displays after, any audio played back (youtube or iTunes tested) would degrade during copy/paste function on the Thunderbolt drive. It did NOT occur on the rMBP when the displays were connected to one port and drive ocnnected to the other port. I believe the rMBP has one Thunderbolt bus, like the cMBP, but the two ports make the difference.

We also observed screen flicker when the order was display=>display=>tbolt drive (I think it was on rMBP).

So, in my case, the extensive testing showed it wasn't the tied to the tbolt displays or the tbolt drive. It was because everything was connected on a single port.

I have the same layout currently on my MBA (tbolt drive=>display=>display) and the audio problem occurs as well.

Update on my situation. I took my MBP 13 in and they sent off for repair. We were able to duplicate in the store but it took a bit of effort. Support replace my main board and returned the laptop and it has been fine ever since. Now, one thing that I NEVER saw before is if I have more than one external drive ( that does not have its own power ) attached I get a low power warning for the USB ports.

The previous main board failed with just the thunderbolt display attached, regardless of additional drives or not. This leads me to believe the original main board barely had enough power to drive the display and now will warn on excessive power drain / use.

That was months ago and I have never had another issue with my display flickering.

So.. whatever that's worth... Good luck.

Same deal here.

Brand new 27" imac stacked with 32gb ram, 4gb gpu, ssd. 27" TB display.

2 days into the kit:

1. Flickering screen 3 times so far unplug/replug

2. Audio that sounds like a far off AM station in the middle of the desert. Behaviour starts about 5 minutes after running any audio app including gotomeeting

I'm ******. All of the same behaviour reported for 3 years now.

This thing is going back.