Farewell to Android
Klout is FarmVille for grown-ups
Does Flash matter on mobile?
What is Twitter?A few months back, I started having problems with my beloved iMac. Lines would appear on the screen, as well as patches of odd color. But worst of all was the series of system crashes I suddenly started suffering, often more than once a day. They'd happen while using Firefox, or opening a stack on the Dock, or just moving my mouse.
I tried disconnecting peripheral devices, used TechTool Deluxe to test the integrity of my hard disk and memory, but found no solution. Looking at Console for a clue (I probably should have done this first), I found lots of serious looking errors occurring just before my system crashes. They all took the form of:
21.06.09 22:25:31 kernel NVDAOpenGL: Channel exception! status 0xffff info32 0x3 Fifo: Unknown Method Error
21.06.09 22:25:31 kernel 0000000b
Now, I may not be a Mac expert per se, but my experiences working with OS X, Windows and Linux told me that "NVDA", "OpenGL" and "Channel exception!" pointed to the fact that something was gravely wrong and that it had something to do with my Nvidia 7300 GT video card. Which begged the question: is this a hardware or a driver issue?
Reading this helpful thread on the Apple Support forums, I've found that plenty of other iMac owners are suffering with the same problem. Consensus there is that it's related to a driver/software fault... but this is confused by there being at least two problems which cause similar issues. User Asrenzo's comment from yesterday helps to clarify the situation. After carrying out various tests, he feels certain that the software/driver theory is right. It seems that OS X 10.5.7 introduced a new, faulty driver for the Nvidia graphics card which simply stopped it from working properly.
"But what about the fix?", you may be wondering. Well, the solution I've found is simple: install Snow Leopard. In my case, I backed up my entire home disk with Time Machine, erased and did a clean install, and then imported my apps, files and accounts from Time Machine. I'm not sure that the Time Machine bit is essential but I can say that not only does my 3 year-old iMac run like new now, I've also yet to see any Channel exception! or NVDA(OpenGL) errors.
If you're suffering with frequent crashes and are at your wit's end (and your Mac's compatible, of course), try doing a clean install of Snow Leopard. It certainly seems to have worked for me.
[...] is the original: Fix for NVDA(OpenGL): Channel exception! iMac error | OnSoftware By admin | category: driver software | tags: also-the-introduction, asrenzo, [...]
yeah..... installed 10.6 on my 24inch 2.16ghz white imac and still get the same gpu errors, still get crashes, gpu still over heats, spinning beach ball, etc updated to 10.6.2 and still get the same errors.
@jon doe - That's bad. I have had periods of crashing on my iMac since I wrote this post, but they are less serious and last less time than before. I think that in the end, there is some sort of hardware issue. I take it you have the Nvidia card too?
yup. 7300 gt. i've been pulling my hair out. it seems to only crash when i am using propellerhead record sofware, though that is mainly because it is the computer that is in my music studio, and that is my main software. it usually crashes after getting some glitchy artifacts after about 30 minutes to an hour of use. then the screen freezes, and often the music keeps playing and yesterday i was still even able to play the midi track that was selected with my midi keyboard, even though the screen was frozen (which requires a hard reset). after much research, some people have found that smc fancontrol works as a fix, but i can't increase the noise when i am creating a mixdown. noise is not something you want in a music studio. some people have replaced the video cards, and several who did (or had apple replace them) still end up with the same problem. i have read a posts about people deleting or changing kext files, deleting the gforce files from the library, trying to go back to an older driver version, etc. i even read a post where one guy suggested putting the GPU in the oven at 200C for 10 minutes! lol! then i read a post from cocoatech: http://forum.cocoatech.com/showthread.php?t=5393 its stated in there (read through the pages) that nvidia acknowledges there is a problem with the drivers, and that they are possibly working on a fix. the post is pretty recent. then i read that way back, possibly a year ago, apple put out some drivers that were supposed to fix something with display ports for gforce cards. those drivers were for a bunch of different computers, including the imac 24, but were quickly pulled within a day or two, put back out for download, and the only difference was that they excluded the 24inch imac in them. this leads me to believe that it is possible that the drivers did not significantly destroy anything right away, but over time caused problems in the imac 24s. we may have downloaded these faulty drivers that are quite literally driving me nuts. i've tried resetting smc, i've tried resetting pram, i've tried disconnecting all devices, i've tried clean install of snow leopard, i've tried just about everything except replacing the graphics card or drilling holes in the back like some 24inch imac users. this really pisses me off because my computer is just under 3 years old. i've had computers last me a LOT longer than that. i'm out of warranty on a really stupid technicality - i bought apple care from an apple store, the girl that sold it to me insisted that i "was all set" and didn't need to do anything else, and that "i just have apple care now" for my imac. then this past week when i called apple they informed me that i'm not under warranty, that i purchased it a month after the one year was up, and they told me that they are going to refund my $170 that i paid for the apple care (which was nice, but still sucks because the repair will cost a lot more if it were to come out of my pocket). had i purchased it within the proper time frame i would have had apple care until mid january. enough time to just take the computer in for service. BUT NOOOOOOOOOO. now that i have done a lot of research on this, i have drawn a few conclusions: *there "might" be a fix since nvidia acknowledges the problem *this IS apple's fault *i SHOULD bitch to apple and make them repair their faulty product (it was never misused and should be considered a manufactures defect) *if all else fails it is possible to replace the card
I also own a white 24" 2.16GHz iMac, which 8 month ago has started to produce the NVDS OpenGL Channel Exception error messages and the screen gets buggy, even the OS frozen. Tried everything, but not yet the VGA board replacement since it would cost half of the price buying another used one. Dismounted and blowed with air duster, etc, nothing helped but was thinking about what it VGA card overheats because under lower load the problem not always materialized. Got the idea: is there a FAN control application available? Found the FREE (!) Fan Control application (http://www.lobotomo.com/products/FanControl) which is a pane in system preferences and shown that CPU Fan (which cools the VGA too!) rotates only 1200rpm. Guess what! I have set it to rotate at a minimum of 2500rpm and since then the logs are clear, no freezing, no buggy screen, etc, even after editing the 100th RAW picture in Aperture 3 (which was my OSX killer app prior...) :) I am testing this method since 2 days, leaving lots of full-flash web pages open for all night and the system is stable. I am happy now (I have used thic computer for a year prior the error ruined my iMac usage), give it a try if really overheating was the cause of the error...
@Balázs - You're right, a fan control program helps. In fact, I should have updated this post to mention that I finally solved the problem with SMC Fan Control (http://smcfancontrol.en.softonic.com/mac) which is also free. Thanks for your comment!
Hello guys! I've had the same problem as you've described above. What I did, which actually even further strengthens the belief that it's a driver issue, was to disable the extension NVDAResman.kext. Since then I haven't had a Kernel Panic. At the same time I can't watch video files on my mac now. But Photoshop works, and that's what I need it for. I haven't tried installing Snow Leopard yet, but sure hope it solves the issue. The guide I followed can be found here: http://www.fuckthisforalark.com/?p=131 Kris
I finally solved the problem.
After months of complete despair I found a solution. Simply rename AppleGraphicsPowerManagement.kext to AppleGraphicsPowerManagement.kext.disable in /System/Library/Extensions. After that, boot with -f argument to rebuild kexts cache.
Well, since I have a MacPro4,1, it didnt solve the problem for good. Reading and doing this: http://www.tonymacx86.com/viewtopic.phpf=15&t=20367&start=0&hilit=Channel+exception
SOLVED!
I also recommend: http://www.insanelymac.com/forum/index.php?showtopic=266036