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

I've made some more specific and revealing discoveries:

I repeated each of the following tests on 2 identical 2011 Mac Mini Servers with the same outcome:

8GB RAM, Thunderbolt Display only - NO FLICKERS

8GB RAM, Thunderbolt Display and HDMI secondary display (Acer AL2216W) - NO FLICKERS

16GB RAM, Thunderbolt Display only - NO FLICKERS

16GB RAM, Thunderbolt Display and HDMI secondary display (Acer AL2216W) - FLICKERS

Both RAM sets are from OWC.

This raises more questions now of course. I don't have an inventory full of hardware to test more equipment.

I am actively in touch with Apple Support who, after already replacing my Thunderbolt display to no positive effect, are now offering to either 1) replace my 16GB RAM or 2) Replace my Mac Mini and Thunderbolt Display.

I will receive a response tomorrow from them regarding the situation.

I have had similar issue on an MBA late 2011 attached through the thunderbolt cable coming out of the monitor. The flicker dissapears when I use another cable and plug in the TB connector of the monitor.

Another thing is that flickering will reappear even in this set-up, if I use the ethernet port of the monitor to connect to teh network.

Just got my 27" Thunderbolt display. I installed the latest Lion update that included the Thunderbold firmware software 1.1.

I'm still getting flickering on my Thunderbolt Display. Interesting enough the flickering only happens for the first 5 min after plugging it in. It seems once the display has been active the flickering goes away. I workaround this by setting my MBA as the primary display and then once the flickering subsides I change back to having the Thunderbolt as my primary monitor. This is not a long term solution and I'm unclear if the specific issue is limited to my monitor.

I'm still hopeful this is an additional firmware issue that can be resolved so I don't have to ship the monitor back. Below is the console log for this morning sorted for "DP Link". I arrived at the office at 7:50 AM.

2/21/12 7:54:12.000 AM kernel: Restoring DP Link

2/21/12 7:54:58.000 AM kernel: Restoring DP Link

2/21/12 7:55:34.000 AM kernel: Restoring DP Link

2/21/12 7:55:36.000 AM kernel: Restoring DP Link

2/21/12 7:55:40.000 AM kernel: Restoring DP Link

2/21/12 7:56:53.000 AM kernel: Restoring DP Link

I've followed this thread with interest as it cropped up on a search. My problem is slightly different but may throw some light on the general problem:

I have a 27" iMac 2.7GHz Intel Core i5 with 16Gb RAM. I'm also using a 20" ACD alongside, a set up I have used with my previous 24" iMac. The ACD is being used as an extended desktop (not mirrored).

I've just started noticing an odd effect: When moving a file from a folder onto the desktop, the entire iMac screen flickers and breaks up momentarily before reverting to normal. It is an effect which lasts a fraction of a second and is visually very intrusive.

Weirdly, if I move the file but continue to hold it for a second before releasing to place it on the desktop, there is no flicker.

Similarly, if I open another folder and place the window alongside, moving a file from window to window produces no flicker. It only happens when moving something to the desktop.

The effect does not happen if the ACD is turned off (but connected) or the ACD is used in Mirror mode.

So … from this it looks as if, in my case, it may be a Thunderbolt PORT problem as I don't have the Thunderport display.

Is this of any help?

After waiting for several months today I called Apple again and the senior advisor that was on my case is no longer a senior advisor 😕 so they transfered me to another "senior" advisor and now they are telling me that the problem is that third party memory so now after dealing with this issue for I don't know how many hours, wasting my time and money now they are telling me that the CAN'T help me if I have this memory installed, I know it's not the memory because it works fine when using only 8GB so right now I'm trying to get my memory replaced to try with a different set of memories and if not I will have to take the manchine (AGAIN) to an Apple Store for further testing.

At this time it's starting to feel like a bad joke.

Same problem with my Early 2011 MB Pro. This started when I upgraded to 16 GB of ram. Today I opened it back up, and just swapped locations for the two ram cards. Either this or the fact that I reseated the ram seems to have stopped this flickering for me so far.

whosyourtator wrote:

Same problem with my Early 2011 MB Pro. This started when I upgraded to 16 GB of ram. Today I opened it back up, and just swapped locations for the two ram cards. Either this or the fact that I reseated the ram seems to have stopped this flickering for me so far.

Hey tator, where did you get your 16GB RAM upgrade for your MBP? Did you replace your original RAM with new RAM, or keep your old RAM, and add additional?

It seems that after dealing with this issue for over 6 months today we finally found out what is causing this issue. I took the machine to the Apple store and there they installed a new set of 16GB of memory and we tested the machine for hours without any problem so while I was testing the machine I decided to call crucial AGAIN (this is where I bought the 16GB) and today they told me after checking my order number that the memories they sold me have an issue, this is exactly what they told me : "I am showing here that is a chipset issue. We have found that the parts you have now may not work properly at max settings". So they are going to send me a new set of memories tomorrow that will hopefully fix this issue.

I will post back after testing the machine with the new set of memories.

I had previously added this RAM when the flicker started: http://www.newegg.com/Product/Product.aspx?Item=N82E16820233251

Still no flicker since reseating and swapping module locations.

This may be off-beam but … As mentioned previously, I have the 27" Thunderbolt iMac with an older 20" ACD, connected via adaptor. Flicker occured when I dragged files from windows to desktop.

I seem to have cured it by changing the desktop image from the Lion galactic spiral to a plain blue background on both monitors. I haven't been able to replicate the earlier flicker effect and have made no other changes.

Is the graphics card accessing RAM or operating at the edge of it's ability when something is connected to the Thunderbolt port?

The only other way I found to prevent the flicker was simply turn off the external ACD.

Thank God, I found this thread!

My setup: Mac Mini Server 16GB OWC RAM, Thunderbolt Display and ACD 20" via HDMI port.

Eversince I upgraded to 16GB three month ago my Mini constantly goes nuts: flickering all the time, sometimes 10 flickers in a row!

What I observed so far, is every time the GPU is on the verge of being maxed out (i.e. the memory usage of the Intel HD3000 is extremely high), the flickers start. Especially when on YouTube or playing other flash content.

- Disconnecting the second display (ACD) helps. Memory usage of the GPU goes down by approx. 50% - no flickers.

- Putting back the factory 8GB RAM also solves the problem.

However, I need the RAM and the second display.

The flickering is indeed annoying, but can be dealt with by just ignoring it. What I am afraid of, is that the flickering somehow damages my computer. I know, it's irrational, but I can't shake off that thought.

Flickering is back under heavy load. Going to RMA this Corsair ram and see if I can find another kind that works better.

Same problem with Patriot brand 16GB total ram in my early 2011 Macbook Pro 13".

So it sounds like all the following ram has this problem. I've personally tried both Corsair and Patriot that specificly state they support my Macbook Pro.

• OWC
• Crucial
• Corsair Mac Memory
• Patriot Mac Series

So the ram manufacturers/resellers are at fault here because Apple doesn't claim that Macbook Pros support 16gb of ram, only 8GB. My guess is that it won't work correctly until a firmware update is released. :-(

Today I got the new set of memories from Crucial and 5 minutes after installing the new memories the thundebolt display flickered again 😟 so I called crucial again and they are sending another set of memories (this time they are sending samsung memories, the ones I got today are Micron), when I was at the Apple store last week I'm pretty sure that the memories they installed on my machine to test it were Sansung so hopefully the new set of memories will fix the problem, if not I will have to buy the memories directly from Apple because that is the only way to keep troubleshouting this issue directly with Apple. Once I get the new memories (Sansung), I will test them and post back to tell you guys the result.