Q: Red and green square dots?

i have a new 27" iMac purchased in Jan 2014.  experiencing the red/green/blue square pixel problem starting the last few weeks.  random.  comes and goes.

anyone else with a new mac experiencing this and have a solution?

I was fighting with my iMac until last week, when the only thing i could try was installing Yosemite Developer update (now on number 4)

The Yosemite could manage better the machine, but the squares and locks on machine wouldn't stop, but minimize.

Observing the machine, i could see that it freeze more when cool then when in heavy use. Everyday i start to use it, it lock some times, even moving a window on screen, then, after some warm up, it turn into usable.

So, today i try something different and unusual.

I put a mp4 video (720p one, with around 150mb) into loop playback. so, the GPU never goes unused 100%. (never could down enough)

And it works. No more square dots, no more lock on, until now.

The thing i think is the problem, is a bad manufacture and a soldering problem, so, when it is cold, the parts retracts and this soldering get with contacts problem. But when it is hot,  the things expand because, and then this bad soldering keep connected.

Until i have a new machine, and then i can put this one to recall/change to another new video board, this will solve my problem.

I hope that could help you all.

Cheers

I too am having this problem, iMac 27-inch, Mid 2010 with a 27" Display. Problem seems to be affecting only the display.

So an update.  I've been dealing with this issue for almost two years.  After Apple replacing the GPU twice and the logic board once, replacing the RAM, i was still having trouble.  In fact it was so bad that i couldn't get a minute past logging in before the system would lock up.    So Apple offered me all the money i had spent at that point to try to repair my iMac returned to me towards the purchase of a new one.  So I bit the bullet and ordered a new 27 iMac.   I wasn't sure what to do with my old iMac.  At first i thought about letting Apple recycle it for me.  But then i thought there's nothing wrong with the LCD so i put it in to Target Display Mode and used it as a second monitor (with a Thunderbolt to Mini-DVI cable).  It worked great!  But now that i had the new one i still struggled with the fact i was able to access my data (via Bonojur/sharing) and use the iMac as a monitor.  It was really bugging me that i had this perfectly good iMac next to me being used as a monitor!!   So I decide what the ****..

I spent a few hours today reflowing the graphics card on the old iMac.  I used a heat gun and replaced the thermal compound on the GPU.  So i turned it on about 8 hours ago and has been on nonstop with sleep/screensave enabled and i've not had any artifacts or freezing at all.  It's like nothing was ever wrong with it. 

I can only sumise/guess that Apple is replacing the Graphics cards with refurbished/old cards?  I don't know for certain but the thermal compound that i cleaned off the card was dried and cracked badly.

So long story short.... a reflow and replacement of the thermal compounds seems to have done the trick!  If you've got nothing else to lose give it a shot!

Just adding a new report of the problem. Mid-2010 iMac, Radeon HD 5750. Problem began in earnest last December, then magically went away, and now is back in earnest. Since the problem returned, I upgraded to Mavericks from Snow Leopard. Just tried the energy save trick and it worked for about 15 minutes. Now I am getting the blocks of bad pixels back again. Have not taken into any repair shops since it's out of warranty.

You all are still reporting from an earlier known problem.  My Mac was bought this year - 2014.  Same problem though.

I did the online chat with Apple and they couldn't fix the problem. Gonna have to take the Mac in.  *****. 

Apple people, do u have a fix?!?!?!

I have had this problem with my Mid-2010 27" iMac with Radeon HD 5750 graphics and running Mavericks since late last year.  The problem was originally fairly mild but gradually increased in severity until I could only power-up and run for a few minutes before everything began to slow to a halt.  So I took it into the local Apple Store, reproduced the problem there and also observed it when they ran from their own external OSX drive.  It was much less severe but still observable with their software and only using my iMac's hardware/firmware.

They replaced the graphics card for $226 plus $39 labor and I've been running now for 24 hours and have not seen a trace of the problem yet.  If it reoccurs, I'll post again here.  FYI, here is what the System Info app says about the new card installed:

ATI Radeon HD 5750:

  Chipset Model:    ATI Radeon HD 5750

  Type:    GPU

  Bus:    PCIe

  PCIe Lane Width:    x16

  VRAM (Total):    1024 MB

  Vendor:    ATI (0x1002)

  Device ID:    0x68a1

  Revision ID:    0x0000

  ROM Revision:    113-B9710C-238

  EFI Driver Version:    01.00.417

  Displays:

iMac:

  Display Type:    LCD

  Resolution:    2560 x 1440

  Pixel Depth:    32-Bit Color (ARGB8888)

  Main Display:    Yes

  Mirror:    Off

  Online:    Yes

  Built-In:    Yes

Hey Guys, i send my iMac 27" mid 2011 with Radeon 6770M to change the video board for a new one on apple support.

The part came and was installed in one week, and in this mean time, i have a machine borrowed from a friend to keep my work on. For lucky.

I pay R$ 620,00, is about US$ 200,00 for the new one, directly from Apple. Labor included. The low price was because they help in price when you put another equal one. If i turn to change to another one, better video, i would payed the full price and lost the guaranty.

I'm using it about 2 week's now, and all is fine and is so marvellous to have a machine that not hang up anymore. Stable.

This is priceless. So, was a problem in the video board. Probably caused by a bad soldering that in time appears and got worst, by heavy use.

I can't wait to change to the new one Mac Pro. I need a faster machine.

for what it's worth -- I restarted using cmd + r - and then did a verify / repair permissions, one of them was for a GPU permission and it was repaired successfully

since then I *knock on wood* haven't had the issue again, been successful for about an hour or so

anyone else try this?

After a few unsuccessful online efforts with apple, I took my late 2013 iMac in to the apple store.  After about 3 minutes they said they would replace logic board (graphics card is on logic board on my mac).   Had to leave at store for a few days for part to come in.

They replaced logic board and LCD display under warranty.  About $1400 worth of parts plus labor.  Zero cost to me.  Don't know why they replace LCD screen, I am fairly certain it had nothing to do with the problem.  Oh well, everything working fine for the last couple of weeks.

I too have the same issue. 27" mid-2010 iMac, Radeon 5750. The issue started shortly after the HDD was replaced through a recall program.

I tried all the tricks listed here without much success. They pretty much lasted about 15-20 minutes each.

One thing that I didn't see mentioned here: I noticed that if I try to take a partial screenshot (cmd + shift + 4) of the issue, the pixels stop appearing in this section. It looks like this "cleans" this section of the screen for a while (a couple of hours in my case). You can see where I selected an area to the left in a previous screen shot.

I'm not sure what this means, or even if it means anything at all. :-)

From what I read, it looks like my only option is to bring it in for repairs.

Have a nice day!

Well, add me to the list.

I have been having the red/green dot problem for quite a while now. After reading on this board that no one seemed to have a 100% solution, I finally gave up and took it to the Apple store to replace the video card.

No difference with the new card, the problem is exactly the same. Didn't even last a week.

I note I've used LogMeIn on this machine, and the logmein sessions have the same dots. I guess that makes sense if the graphic board renders the display.

Not sure if I'll try the more expensive logic board, or just cut my losses.

This is a 27" iMac mid 2010 unit with the 5750 Radeon card.

Cheers!

mine has progressed way beyond red and green squares, not sure what to do

Hi there. Just a quick note to say thanks. It sounds like a lot of you have gone through a lot of pain, but through your sharing it seems, at least so far, I have been able to resolve my problem.

I am sorry I am not 100% certain of the exact steps (specifically when I was in safe mode vs normal) I took but the general gist was;

I had the green/red "dots" reasonably evenly distributed over my late 2009 iMAC 27inch.They just came up about 3 days ago.

I turned the setting "put computer to sleep" to "never" and unchecked put hard drive to sleep, then after some time rebooted. The dots disappeared.

Unfortunately, the next day when woke the computer monitor up the dots were back.

So (in safe mode now I think as I could not boot) I turned off put monitor to sleep then started converting all my saved TV shows from eyeTV to a format I could get them off the iMAC -as I really was not that hopeful anything would work. I am not sure when but time I next looked the dots had gone.

Several days later dots had not come back- but I was still in safe mode.

I was having trouble being able to boot up not in safe mode (would get stuck at the grey apple icon). I read up that I should remove all the USB connections
(eyeTV, bluetooth connection for FitBit, FitBit recharge connection, also my powered speaker) and restarted.

I did this and was able to boot up not in safe mode- and still no dots.

Will come back in a couple of days and let you know if still ok.

I have the same issue i dont have the money to replace my graphic card so i try thinks..

1. open mac and clean from dust

2.try replace graphics card firmware to previous versions (not allow me)

3.open in safe mode (holding shift) search things over an hour and suddenly when i move a window from left to right lines erase like i have the window as eraser tool..

I m disappointed from my mac coz i pay 2000euros for this machine and i expect to have it without problems and spend money to replaces like windows user do apple dont answer to anyone about this, and i search there are hundred  of users have the same issue. Now i am cautious about what am i doing with my iMac i don't even install ps after effect etc...

I have 27-inch, Late 2009

Processor  2.8 GHz Intel Core i7

Memory  16 GB 1333 MHz DDR3

Graphics  ATI Radeon HD 4850 512 MB

Software  OS X 10.9.4