Q: 2011 i5 2.5Ghz Mac mini screen flicker issue...

To get to the bottom of the issue either being an OS X driver issue or an actual hardware issue, its time to do a test under Windows 7 (or XP).   Set up bootcamp, install Windows and get the latest drivers from AMD.  If it goes away under Windows 7 with the latest ATI drivers, then its likely to be the OS X driver.  If the problem still happens under Windows 7 then its likely to be a hardware issue.  Either a cooling issue or a defective GPU.  My 2011 Mac Mini is the server version (Intel built-in graphics) so I can't try out the test myself but this is exactly what I would do to find out.  If its an OS X driver issue, Apple will fix it... eventually.  If its hardware then its more serious and Apple will need to replace it under warrenty.  Hopefully after they replace the potentially defective chip batch in manufacturing production if hardware is really the cause.

Hey,

I installed Windows 7 and the result is same! I tried with all 3 models of Mac Mini and able to produce the same  result with new 27" Thunderbolt display at the local store too! I tried with 4 Mac Mini replacements with Thunderbolt diapplay along with customized Mac Mini. As per AppleCare, it's look like a hardware issue in Mac Mini 2011.

I can confirm that Apple is seriously working on this issue. I got the following response from Apple:

This is a follow up to the case "Mac Min (mid 2011) Graphics Flicker with 27" Thunderbolt Display." After further investigation it has been determined that this is a known issue, which is currently being investigated by engineering.  This issue has been filed in our bug database under the original Bug ID# XXXXXXXX

Apple just released EFI firmware update v2.2 to MacBookAir. KB: http://support.apple.com/kb/DL1448 It resolves major display issues including Thunderbolt display. We can expect a simial firmware update for Mac Mini too.

I installed the latest EFI firmware the other night for my brand new mac mini and no joy. If anything its worse. Its going back to the shop. I presume there should be no issues getting my money back, since its been less than 14 days.

But really annoyed at Apple. They must have known about this issue yet no one at the store or anywhere its advertised mentioned it.

I had sold my mac book pro to buy the mini. Which now means i will have no MAC!!! As a developer who relied on a MAC to earn a liviing this is really bad for me!!!!

Well,

It's a known engineering issue. I suspect this related to "Thunderbolt Software Update v1.1 (for OS X Lion)", since the latest EFI firmware update v1.4 fixes the issue. But the same behaviour came back again after I installed the above mentioned Thunderbolt software update. I reinstalled the OS X Lion from Internet Recovery and didn't installed the software update again. I can confirm that this resolves the flickering issue for me.

When comes to returns,

You don't need to worry about 14 day return option. If you contact AppleCare or local Apple Store Genius regarding this or similar issue and if Apple didn't fix the issue in life time, you can safely return the product for full refund.

In my case i'm testing the new Mac Mini EFI (v.1.4) + Thunderbolt Software Upgrade v.1.1 + Firmware for 24 Cinema Display

http://support.apple.com/kb/TS4045

"LED Cinema Display (24-inch, Late 2008): Intermittent flicker while connected to a Thunderbolt port"

I believe my mac mini (mid 2011) is stable now. 8 hours of use without flickering or black screens.

Any lagging when you open or navigate launch pad? Did you connect Mini to Thunderbolt Display using default cable or separate cable to connected to second Thunderbolt port?

I have experienced the dreaded sreen flicker issue on 2 different Mac mini's now (2011 and 2012 versions).  I may of found a fix so I'm posting here to hopefully help others.

Basically there appears to be an HDMI copyright handshake issue that is causing the problem.  Both of my Mac Mini's would flicker every 5-6 seconds where the display would go black and then re-appear.  After talking to Apple Support the fix appeared to be doing an SMC reset as well as a PRAM reset.

SMC reset

http://support.apple.com/kb/HT3964

PRAM reset

http://support.apple.com/kb/HT1379

This solution worked fine for my 2011 Mac Mini but not for the 2012 Mac mini.  I found that I had to completely disconnect the HDMI cable, and THEN do the 2 above resets.  THEN reconnect the HDMI cable.

Hope this helps others!

***My Mac Mini's are connected to a home theatre setup and my displays are a Sharp 80" (LC-80LE632U) and a Mitibushi FD630U Projector.  After futher troubleshooting, Apple's HDMI handshake appears to have some issues with the Mitsubishi projector.

My mac mini started to flicker more than 5 to 6 times in a minute which was frustrating, I solved this problem .

The problem started when I kept my mac in vertical standing position which imposed stress on the cable, so the position of then mac may effect your cable.

What I did is first disconnected the cable from mac mini then removed my dvi cable from the adapter, then I straitened the cable so that it does have any twist and turns which might have occured earlier.

Then I connected back and voila no problems and flickering is gone. I guess for there are two problems which create flicker in macs one is the cable and second is the software.

Try this if you have problem, if this still does not solve, try with another cable and if the problem still persist then it might be the software one.