Is my NVIDIA GeForce 8800 GS graphics card bad?

I started my iMac up in the Recovery Disk mode so I could use Disk Utilities to wipe my drive. Then I used the install OS X [Lion] option to install the operating system.

I thought that fixed the issue because the screen saver [Flurry - at default settings] was performing much better after the wipe & re-install. Then, while doing some basic tests, the problem sprung up again while trying to drag & drop a wallpaper from a web page in Safari to the desktop. This time there was much screen flicker and strobe-like pulses in horizontal bands across the bottom half of the iMac's screen before the whole screen went to a mustardy shade of yellow. Followed by a manual forced shutdown, of course.

Absolutely right about that... Nothing to lose here.

As soon as I get a chance, I'll give that suggestion a go.

:)

Well, it was worth a shot. No joy, though. The screen glitching still occurs and after looking at the Console log, judging be the number of this repeating issue in the report:

"

4/15/12 9:44:21.000 AM kernel: NVDA(OpenGL): Channel exception! exception type = 0xd = GR: SW Notify Error

4/15/12 9:44:21.000 AM kernel: 0000006e

4/15/12 9:44:21.000 AM kernel: 00200000 00008297 00000474 00000010

4/15/12 9:44:21.000 AM kernel: 0000047e 00001458 00000006 0000000b

4/15/12 9:44:21.000 AM kernel: 00000000 00000000 00000603

4/15/12 9:44:21.000 AM kernel: 00000010 00000000

"

I'd guess it sends that error from the "kernel" for everytime the screen glitches/flashes.

If I understand this right... The video card's OpenGL is throwing some kind of exception - which I understand to be really bad, right?

"0xd = GR:SW" - I have no clue what this means.

All of the number groups, like "0000047e 00001458 00000006 0000000b", represent [video] memory locations, right?

This is a pain because the hardware still checks out as "ok" and the only software I've installed and run to "torture test" the issue is Starcraft II (which I've played [at lowest graphic settings] since its release, what two years ago, without incedent). Although I've had the problem occur using Safari, Pages, Launchpad, and just moving things around in the Finder, so I don't believe the problem is confined to one specific application.

Hmmmm.... [still thinking]

Sure. I suppose I could try the Snow Leopard OS. I was an early adopter of Lion and hadn't had any problems up until about a month ago. The last thing I remember updating was my copy of SkethUp Pro; however considering I've wiped my drive and started from scratch I'm still stumped on this most bizaar problem I've ever had with any of my Macs.

Of course, having said that, considering I've exhausted my reportorial of troubleshooting techniques (Mac user since the early-mid 90's [ xD ] the only thing I can think of that I'd love to have access to a spare NVIDIA card to swap out and see if that works (I understand that's possible w/the 24" iMac that I have). I'm just not convinced I'm ready to drop $350-$550 on the off chance that I may not entirely be a graphics card issue. At one point I cruelly considered it may have something to do with the audio because when I kept the system muted, everything seemed to work ok... But then not really (hahaha!)

Thank you for all of you help and feedback so far though!

:D

The Snow Leopard idea didn't pan out for me either.

The RAM is the same 4 GBs that I opted for when I purchased the machine back in 2008. Techtools Pro 6 says that the RAM is doin' great. In fact it says the video memory "passed" its test. Too bad it's not more forthcoming with the details of that test, but maybe there's not a whole lot to report on. The only issues that TtP6 reported on was the SMART status of my hard drive - some search errors, temperature variance [test] failure, and some large file fragmentation ( which I found to be really odd considering I wiped the drive an started from scratch - I figured everything would be all neat & tidy w/ such a clean start - xD).

At this point, I'm anxiously awaiting news of an upcoming iMac model refresh.

... I'll have to go check, but I wonder if the RAM in my current iMac would be compatible w/the newer models... Knowing my fortunes... Probably not.

Thank you for the suggestions. You wouldn't happen to understand the code from the Console would you? This whole experience is a waste if I can't learn something from this problem in case I encounter it again. I'm not use to running into a Mac problem that can't be identified in some way or another.

I've been checking into as much information I could stand to regarding this error of mine and have been considering getting a new hard drive for my iMac. I'm thinking it's possible that there could be something in the drive that's causing the malfunction - like putting your car in a parking garage and then forgetting which level/section you parked in.

I've even read Apple documentation that points towards a kernal panic, which I have seen 2 time within the last 1.5 years (at least 6 months apart)... But the general consensus on that seems to point to a RAM issue.

Sadly it seems that I'm getting to the point of $100+ here and $100+ there...

Oh, well. I'll probably be getting a new drive within the next week or so. If this seems to work, I will post an update for anyone else experiencing similar issues.

Unfortunately, no. I've all but stopped using my trusty iMac now. A few days ago I was deleting some files in the trash can and the screen just went black. Of course I had to force a shut down... Send the prompted report to Apple... Then the screen turned a solid pinkish color... And I almost put my fist through the screen.

The most frustrating part about this all is that even after taking my iMac in for testing at my local authorized service shop, they couldn't find anything wrong with it!! If I only knew what was the source of the problem, I'd at least have the solace of knowing what needed to be replaced. The only indicator that points to anything is the Consile readouts reporting an issue with the NVIDIA card just prior to the problem occurring. That sounds good and all, but it's not a certainty. I don't want to spend $350-$500 on a replacement video card only to have the problem persist [because of a motherboard, RAM, etc issue(s)]. I guess I'm waiting for that supposed iMac refresh later this year.

It's a real shame that for all of the reports that I've sent to Apple following this problem with my iMac that some tech genius there hasn't responded with some helpful insight into the problem - I find it really, really strange that I've run the gamut of testing an troubleshooting possibilities just short of removing each possible piece of hardware potentially involved in this epic fail and having them individually tested somehow. ...Even though all the tests give no indication of any problems, and yet, clearly, my iMac is broken. I really expected this machine to keep running a bit longer than the 4+ years I've had it, after all, the "Bondi" I bought many [many] moons ago still functions just fine!

[sigh]

Just out of curiosity [as I may try to replace my NVIDIA card] how much did your replacement card cost and from where did you find one?

I saw where there was a replacement program for the NVIDIA card in one of the laptop models from a few years back...

Would be great if such a program existed for these iMacs!

xD