27" iMac Stuttering Graphics Problem

[cheesygrin]

Hi folks

Got a problem with my late 2009 iMac (spec in my sig). It recently developed the flickering display issue that was a known fault with this model. Sent it back to my local authorised Apple dealer who fitted a new display under AppleCare warranty. Got it back a few days later this last Thursday.

OK, so the new display is fine – bright, colours look great, no flickering. But the graphics are awful. As in, when doing something graphically intensive, they stutter as if the machine is overheating or something. I was halfway through Dirt 2 when the machine went in – it used to play great for an hour or more easily. Now the game is totally unplayable – even in the first race.

So I thought maybe the new display was brighter or something and taxing the graphics more. So I turned the brightness down to half, installed iStat pro to monitor temperatures and installed SMC Fan Control to force the fans to speed up and keep the temperatures down. Temperatures don’t seem too bad now, but the graphics are just as bad.

I’m guessing I’ll have to haul my machine all the way back to the Apple store again, but to save me the hassle, I wondered if anyone had any ideas, or had experienced something similar themselves?

Thanks guys.

 

[derbothaus]

Were you ever able to play Dirt 2? You have a very low specced GPU on your iMac 4670 or 4850. Either one has only 512MB memory. Reduce your res if you are even attempting native or even 1920x1080. Lower all the settings until it works smoothly, especially AA. You don't have the memory for it.
You can't really take a computer back and have Apple make it magically more powerful. You need a more powerful GPU.

 

[cheesygrin]

Thanks for the reply derbothaus, yes I was halfway through the Dirt tour and it worked beautifully before for an hour or more of high res gameplay.

You are right of course, in that the 4670 is fairly low spec, and in fact only has 256 MB of RAM. It managed the game just fine before the display replacement however.

 

[iSayuSay]

What display replacement? Was it the famous smudgey/cloudy/dirty lcd on your iMac?

Hmm if that's the case. I think you should take it back and have them recheck the cables and connections inside your machine. GPU should perform identically over time.

 

[cheesygrin]

What display replacement? Was it the famous smudgey/cloudy/dirty lcd on your iMac?

No, it was were the display flickered occasionally. It was a known issue on the 1st gen 27" iMacs.

You may be right though; could be a loose cable or something from the work it had done.

 

[cheesygrin]

Update: Ended up wiping my iMac and reinstalling form scratch. A few weeks down the line and I've not had any more problems up to now. Looks like it was just some sort of a software glitch from having the new display fitted...