there was a post earlier mentionning tiled desktop images. your artifacts are on the background and dockshadows. You should try changing it as a first step. just in case.
Those artifacts are graphic card related. There was an issue with SnowLeopard and some 2009 iMacs. Keep checking the forums. if you see a lot of complaints, Apple will be working to fix the driver issue. If no one is complaining, I'd say your card may be flaky.
formatting won't fix it.
Happens to me too. Quite random for the most part, but the last few times it happened was during HD video playback (on Quicktime, vimeo/youtube).
It would start out as random flickering of artifacts on the video then suddently the entire screen would get affected.
Mid 2011 iMac 27", i7 6970m 1gb
My 2008 Intel iMac (under Lion) was working perfectly until last night.
So yesterday night, the screensaver appeared (it's the one with Nature pictures), like it does usually.
After a few seconds I noticied that every picture was followed by a kind of "white flash". This was really frightening.
So I moved my Magic Trackpad in order to go back to the Desktop.
And then, artifacts appeared on the top right corner of the screen, "printed" into the desktop background.
I rebooted immediately and haven't to face this issue anymore yet, but I feel like I can't rely on my iMac anymore...
(sorry for my english)
Just today my new iMac i7 has started to get artifacts on icons and menu items while playing flash video and when doing some video rendering (so 100% CPU). It looked very similar to the problem I had with my old Macbook Pro when it got hot.
I installed the "desktop monitor" software and the GPU Diode is at 78'C, the GPU heatsink is at 72'C. They are the two hottest components in the machine. The top of the case is too hot to touch and the fans are no where near being at 100%, they are only running around 1400RPM.
I suspect this could be another issue where Apple have set the fan speeds too low to keep the system cooled sufficiently. I think I may take out AppleCare extended warranty as I lost out when my MacBook Pro finally failed because it was out of warranty.
Yes, I could install SMFanControl, but I'd prefer if my Mac did the job it was designed to do without having to mess around with third party apps.
My iMac has all the vents completely clear, and although it is a warm day it's not excessively so.
Right, an update. Ambient temperature is 21'C, GPU Diode was at 79'C and GPU heatsink 75'C.
Installed SMCFanControl as I wanted to test the idea that it was heat related artifacts from the GPU, once all fans at 100% and with all internal temperatures below 45'C - GUESS WHAT! No more artifacts.
I'm going to leave the fans at 100% as I don't want to damage my brand new iMac when I'm rendering video. I'll keep an eye out for recalls/fixes/exchanges though as you don't know what damage has already been done to the processors / PCB's.
Yeah, had the same thing in Console logs, and of course I meant i5 not i7
Model Identifier: iMac12,2
Processor Name: Intel Core i5
Processor Speed: 3.1 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 6 MB
Memory: 4 GB
Boot ROM Version: IM121.0047.B0A
SMC Version (system): 1.72f1
Chipset Model: AMD Radeon HD 6970M
PCIe Lane Width: x16
VRAM (Total): 1024 MB
Vendor: ATI (0x1002)
Device ID: 0x6720
Revision ID: 0x0000
ROM Revision: 113-C2960H-188
EFI Driver Version: 01.00.544
I have a 2006 24" iMac. I've been getting artifacts, as well as occasional screen freezes (lasting about 20-30 seconds). Sometimes the screen freezes during video playback, other times when I'm just navigating around my system.
Interestingly, when the screen locks up I've had audio continue to play even though the video is stuck.
I've installed SMCFanControl and I'll tinker around with it to see if it helps.
Thanks for the idea.
I think this may very well be related to the other Lion (iMac 2011) freezing issue: https://discussions.apple.com/thread/3194165
I noticed artifacts in my menubar after watching a video on YouTube (which was flashing green intermittently). From what I've seen in the other thread, they get artifacts too as well as the freezes.
If they're related then it's likely a driver issue with Lion and these latest iMacs.