Q: New iMac 27inch screen flickering/tearing/shutoff

Hi Guys

I had a similar flickering problem with my new i7 pc, I have the same ATi card as the Imac 27 inch.

I resolved the issue, it was the ATI catalyst software along with the latest driver, I uninstalled the latest driver and catalyst software and just used an older version of the ATI driver, havent had a problem since.

Hope that helps.

Cheers

Also

Sleep mode wouldn't work properly either, but was fixed with older Ati driver.

Cheers

where did you get the older drivers??

Check the ADM site ( http://support.amd.com/us/gpudownload/Pages/index.aspx ) for them. Looks like the latest driver only goes up to 10.5 for Mac. Problem?

my experience:

Today I called Apple Care, they told me to upgrade to 10.6.2 and to reset SMC (I think that is the name). After doing this two things and without power it on, I plugged the computer to a different plug (not a strip).

By now I haven´t seen the f* issue again.... but I will keep you informed.

The ATI drivers that come with the OS Upgrade are:

ATI4600Controller 1.6.6.25 (7429)

Best regards from Spain

Guys I have just came back from a store with my replaced iMac. Finally after one week I have decided to get a new one. Hard to say after it has been only few hours if this one is ok. At this moment no problems at all. I will keep you updated so then we see if it is software or hardware issue.

Hi, I bought yesterday a new iMac 27", and the same problem. After update it to 10.6.2, it worked better but finaly, today again the screen splited leaving the dock at the top.
I have taken it back to the store, and got my money back. If I had wanted that kind of problems, I had bought a PC with Windows Vista for 300€....

Take a look to youtube website, and search for "imac flicker" and you will see the same problem you are suffering...

I think it could be the video card.

Bye.

I went in to the Mac store in Glasgow to speak to them about the problem. Said never heard of it and to bring the machine back (it weighs a ton and I need to travel 60 miles with it on a train etc) and if they found a fault they would exchange it.

I explained that I was concerned that I would just be back the following week with the same problem and asked if they could check with head office etc to see how wide spread the problem was and to see what they planned to do about it and was told "no". I could take it in or send feedback to apple.

Not the level of service I expected or was promised during the sales process.

I spoke with 4 different guys from Apple. All of them have not heard about this issue before. That is what they have said anyway. I do not really believe it anyway what they have said to me was information that there is 20% faulty iMacs. I am still wondering if you know anybody in person who bought one and do not have this issue. I do not think they would ever visit this discussion group. By the way 5h after I have replaced and still no problems.

Is this a power issue?

So, I reset my PRAM or whatever it is called (option, command, P, R) and the issue went away. The next day upon power-up, it occurred again. So I reset my PRAM and the issue went away.

One of the things that the support says is that if your computer doesn't remember the PRAM settings, then it's due to a power issue.

So, I unplugged my iMAC and then plugged it in very firmly and evenly. Then I switched power plugs on the switch. It used to be plugged into the label of "External HD" and now it's plugged into the "Computer" strip. (Do power strips give different amount of power to different plugs?). Since then, the issue has not recurred, even through different restarts.

Will keep posted as I LOVE this machine and would just want it to work perfect.

Here's a new development that I don't recall reading here. I put my iMac to sleep last night about 9PM and when I woke up early at 3:30AM, I noticed that the screen was lighted. It woke itself up for the first time and the screen was flickering away. That was it for me. I restarted and, of course, the problem went away for probably a day or two. What made me finally call Support is that the iMac was sleeping with nothing plugged in so there was no external source to wake it up. The "Support Advisor" was very familiar with the problem and acknowledged that the engineers were working on it, but had no solution at this time and had no idea when they might have a solution. So...I decided I didn't want to deal with this issue any longer on a new machine and, hoping that the problem is related to the ATI 4670, decided to order a new iMac with the ATI 4850 and, as long as I was doing that, take an even bigger chance and order a Core i7 as well. So now my $1699 cost jumped to $2199. Here's hoping this problem doesn't affict the new quads with the 4850.

So to update, I have been running 10.6.2 for 4 days now and not a single flicker or anything. Starting Arabesque does not make it happen for me, so I would be interested if anyone can highlight what actions they perform that might make the problem appear again?

Also, is there anyone with problems who isn't using Parallels or VMWare? I use VM Ware and others have made comments about running windows through BootCamp and stuff. I was wondering whether the issue is caused by VMWare?

My flickering problem had started at the first ever start up. Right out of the box as I was typing my account user name. So no, I don't believe Parallels or VMWare to be the issue.

Day 2 since the clean install and new OS. No flickers.

Thought I give an update on my situation:

I have the 27" with the ATI4850. I noticed a flickering on the 2nd day that I had the iMac (still with the standard install, no apps/files moved, OSX 10.6.1). The screen turned for half a sec grey with horizontal bars. Then a couple of days no issues.

Then I had to bring the iMac to the Apple store because of a crack in the glass panel. Once I came home and turned the iMac on again I experienced the black flickering until I did a reboot. Since then (over a week with min 8hrs of working with it) no issues.

The only thing that the two occasions had in common was that the iMac was in cold environment before starting. The first time, I forgot to close the window and it was quite cold in my office when I turned it on. The second time the Mac was cold because I had to carry it to and from the Apple Store.

I will try to give it the "cold" treatment again and see if this is causing the issue. Because all other methods described here to trigger the flickering won't work on my iMac.

From the original setup disks.

I had a brief search for any older MAC drivers but it might mean that due to the Imac 27 being a new machine and only now using these older 4xxx cards it only has the latest drivers, not sure where you might find them or if they are available.

Sorry guys this has only been my exprience with a PC but it seemed so similar.