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I have had the problem for a while, exactly as many here have described: flickering, always from the top of the screen down (different amounts each time), for a split second, and only when using the low-power graphics chip. I cannot confirm about the low-light issue. When it starts happening, it can happen two or three times in a minute, though it often stops for several minutes at a time.
I only noticed it more in the last several months, not when I first got my late-2008 MBP. I hoped it was a software glitch, but Snow Leopard did not correct it. I finally took it to the Apple store in Ginza here in Tokyo; they did not seem to recognize the issue (or just didn't acknowledge it to me), and offered to replace the logic board and monitor. I got it back this afternoon--and just spotted a flicker. Only one, but it means that the underlying problem still exists. (Not that I mind having fresh equipment! ...assuming they didn't give me refurbished.)
It seems to be a general design flaw (darrylh on page 8 probably nailed it)--else I don't think so many would be experiencing the exact same thing. I hope the "control, shift and eject" keyboard action will do the trick when the problem resurfaces. I wonder if this is something that can be addressed with a fix to the OS or the firmware.
I have had the random blinking issue on the 9400M and occasional random hard lockups on the 9600M GT. I've replaced the Apple-installed RAM with Apple-qualified 3rd party RAM and the issue persisted. I noticed that the voltage on my battery tended to drop and spike, so I bought a replacement battery. I haven't had a hard lockup nor have I noticed any blinking since replacing the battery, although it's only been a day so far.
The battery checked out okay at the Apple Store, but their diagnostic only checks the battery at one point in time. I figure that the battery might not provide consistent performance and that the blinks/lockups might be due to fluctuations in its performance.
I'll keep everyone posted but seeing as how some people's laptops might be old enough to warrant a battery replacement anyway, you might want to spend the money on one and see if it alleviates your problems.
I have exactly the same problem as others are reporting, so count me in.
I'm not too pleased, since this MBP just went in to have the hard drive replaced after it died on me, only 6 months after purchase. Apple's support is second to none, but I feel I have right to be annoyed that an expensive laptop fails after 6 months, no matter who I bought it from. Also had 2 iPhones die on me through no fault of my own. Now my screen flickers - it just happened as I was typing - it's infuriating!
I started having a problem with the brightness of my screen suddenly fading down a few levels while working, when the light in the room is dim. Then it begins to slowly pulsate brighter and darker, similar to the "sleep" light near the latch. Apple couldn't reproduce it when I left it there, so they didn't do anything. It's still happening, even as I'm typing this. MacBookPro 15" late 2008.
Any suggestions from anyone? Any resolutions? New to Mac.
I had the same problem as described with brief flickers in various light conditions, with or without outlet power, and with the graphic card on. None of the OS updates helped reduce the frequency or any other symptoms. The "control, shift and eject" keyboard trick never worked.
I filmed my flicker several times. Yes, that's how regular it was.
When I brought it into the Apple Store and showed them the video, they immediately acknowledged the problem and told me it was my logic board. Since having the logic board replaced, I've had no problems.
Take your computer in for service, if you have screen flicker.
Hopefully I can shed some light (no pun intended) on the backlight flickering issue at low brightness. I have designed fpga controllers for LCD panels, and the issue is a combination hardware/firmware issue.
I purchased a uMBP in October and never saw any backlight flickering at low brightness with either GPU. I just received a newer uMBP and it shows the backlight flicker problem only on the 9400. It was immediately obvious what the problem is. The LCD panel has an underlying repetition rate as does the LED backlight controller since it uses PWM techniques to dim the lamps. Apple did not provide enough filtering on the LED PWM controller so the LED's are actually slightly flickering on their own at the rate of their PWM controller. This is not a problem on it's own as the PWM frequency is always high enough that the human eye can not perceive it. The problem is when this frequency or it's harmonics are close a frequency of the LCD, patterns will be created in the light intensity called beat patterns. Since these beat patterns are dependent on the absolute frequency of the LCD and LED PWM, and since each GPU and the LED PWM are sourced from different clocks, the issue will be different for every motherboard, and will vary with such things as voltage and temperature.
I verified my suspicions by slightly shifting the operating frequency of the LCD (not something anyone can do) and the problem went completely away. As I continued to change the frequency the problem would reoccur and subside as the two fundamental frequencies would beat against each other.
The solution would have been to provide better filtering of the PWM supply, but this is a typical trade off that even I would have made when designing a PWM dimming circuit. Also, typical white LED's have a fairly slow response time, so this was probably relied upon for some of the filtering. The other solution is to just shift the frequency of the LCD or LED PWM so that they don't beat. The problem here is again with the absolute frequency (over time, temp and voltage) on each motherboard.
So the bottom line is an LCD replacement will not affect this issue at all (although it may address some of the other issued raised in this thread), and a motherboard replacement is a hit or miss proposition at best, (unless Apple has made a hardware changed, but based on my new uMBP, they haven't) and even if it does appear to fix it at first, it may return later. My guess is (and this is only a guess) a firmware change could be made to shift the clocks to alleviate this problem. This is something I have done to my firmware designs, but is not always possible for other engineering reasons. Certainly the LCD clock rate can be shifted easily, but what complicates the solution is it needs to be universal across all notebooks and that can be a difficult thing to achieve.
So can anyone confirm that they have spoken to someone at Apple that has confirmed they know of the issue and are actively seeking a solution? Without this confirmation, I don't intend to send my MBP back as it can be a futile exercise as pointed out by others in this thread.
I have written this quick note to thank you very much for having posted this information. It has been very helpful!
me and my friend have another issue with flickering, but it is a little bit differnce.
Sometimes for a while we saw just one or two short line into the screen. Every time in a different position. Usually it's a white line (sometimes black), 1px of height and no so much long.
For my friend it happens very frequently, once every 10minutes, for me it's rare.
I have osx 10.5.6, he has 10.6.2
For the apple care is just a software issue, and they suggest to install again the system through archive and install function (or similar).
He tried to switch from 9400 to 9600 with best performance, and it seems to solve the issue.
What do you think? It's a software issue? Firmware? Hardware? Is it similar to the other kind of flickering described in this topic?
I had those lines flashing across the screen when I bought my mbp last autumn. I got my screen replaces due to another issue and after that I had the whole top part of my screen flashing.
What I understood from the repairman is that if the screen flashes with both GPUs then it's due to faulty memory. Mine of course flashed only with the 9400 so that doesn't help.
I raised the issue during last week end when I worked with photoshop and bigger file (from 200mb to 1gb). Black lines flashing, and twice time all the screen became black for a moment.
When I closed the image the computer back to work fine.
Anyway I think that is not acceptable that a computer sold for 2.200 euros could be affected by issue, an Apple doesn't do nothing.