I believe everyone is looking for this thread:
https://forums.macrumors.com/threads/251352/
By the way, I was the one who started this whole thing about the graininess issue, although I didn't start the thread. (I started threads at MacNN and Apple Discussions and someone else decided to post here after).
It's not a software fix. The ATI issue was clearly not the same problem as I've seen photos of computers that suffer from the ATI dithering problem. Apple just chooses to use screens with a lot of anti-glare coating. If you look at the 24" iMac, it almost looks a bit shiny even though the screen is matte. I believe the 24" iMac has less anti-glare thus looking smoother. However, the 17" iMac and 20" iMac have the grain and so do all the Apple Cinema Displays.
Here are the computers that I've seen without grain:
MacBook (Black and White)
iMac 24" Only
MacBook Pro 17" Only