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

I'm one of the original posters in this thread (post #6) and am happy that there might 'finally' be a fix for this issue.. I just applied the update and will post my results in a day or so of use. My fingers are crossed!

-j

techvigator:

About this Mac > More Info > Graphics/Display

Look at Resolution. Should display refresh. however LCDs don't scan like a CRT, so you should not be seeing that effect.

Do you use fluorescent lighting?

My thought is before end up with "the flicker it's fixed" we need at least 2 weeks without anyone reporting the problem on his (new) iMac 27".

Note: the artiste, dxgriffiths are still affected by the problem.
.. and i'm still sitting here waiting for a "yellow tinge and flickering does not affect anymore the new 27s" for safely buy the i7.

Displays:
iMac:
Resolution: 2560 x 1440
Pixel Depth: 32-Bit Color (ARGB8888)
Main Display: Yes
Mirror: Off
Online: Yes
Built-In: Yes
Connection Type: DisplayPort

I've a 27in iMac with led backlit display.
It does not report refresh rate information (i.e. pixel latency)

Eric Cote wrote:
..however LCDs don't scan like a CRT, so you should not be seeing that effect.

Do you use fluorescent lighting?

Yeah, the most similar thing to refresh rate in LCDs is response time, which describes how many times a second the backlight pulses on and off.
The flicker effect could be caused by the LED backlight in LCDs.

There's another thing we could call "refresh rate", and it's frame rate. This is how many times a second the video card "draws" the screen (check the link on wikipedia about double buffer in computer graphics i posted before).

Correct me if i'm wrong.

Ettore,

if the firmware update involves display management I will suppose that my illusion could be due to a different led pulsation but since, as I think, the firmware update could have changed the display interface information, the graphic card/os should adapt the display output (i.e. display port) to feed a monitor with new default refresh rate (as stated by the new firmware) as red by the digital interface of the graphic card.

I see.

It's most likely 60Hz on a digital link.

that being said, refresh rates are irrelevent for LCDs. they apply to the video card signal. there is no vertical electron gun scanning involved.

Flicker is possible on LCDs, but is usually caused by voltage imbalances, not refresh rates.

see here:

http://www.lagom.nl/lcd-test/inversion.php

Figure 7A flickers

Does anyone have done the firmware update of the display panel?

Gene Stienberg wrote:
Maybe some before and after measurements?

Peace,
Gene

I can confirm that with that program under rosetta i5 27" refresh rate reports 60 Hz both out of the box and after both upgrades.

That would mean that the perception of change may be just that -- a perception.

Oh and by the way, no less than The Wall Street Journal is reporting that Apple says it did not halt production of the 27-inch model:

http://blogs.wsj.com/digits/2010/02/02/the-mysterious-imac-delay/

Consider, also, how often PC makers will stop production on a model that proves defective in some fashion. Or has to release firmware updates to address a display glitch. It happens, of course, but nobody pays attention. Nobody pays attention unless it happens to Apple.

Peace,
Gene

techvigator wrote:
Does anyone have done the firmware update of the display panel?

Me

Have you noticed anything strange after that?
By now my iMac has not yet flickered.

Just checking in. Posted several weeks ago - a couple days after I received my week 52 iMac 27" i7. I had one flicker incident (i.e. - small band upper third, then bigger band lower third, then blackout). Thought at the time that it was hardware issue so if it happened once then I must have a defective unit. It didn't happen again, but I always expected it to come back since I was convinced it was hardware. This new firmware update signals that it may in fact be software (or hardware issue mitigated by software). If either is the case, I will rest easy knowing that I don't have to part with my new favorite toy.

I am curious to know what these firmware updates are doing and whether performance is hampered in any way, like slowing up graphics processor, increasing fan speeds unnecessarily, etc. I haven't noticed anything - display is gorgeous as normal, but I wouldn't consider myself a power user so not sure I'm a good judge.

Anyway, I'm a happy camper at the moment so won't be returning to this thread unless I experience another problem. This is hands down the best computer I've ever owned. If you are still experiencing problems, here's hoping for quick resolution so you can enjoy the Apple experience that I've come to know and love.

Dave