I recently purchased a new iMac. The spec is as follows: 3.2GHz Quad-core Intel Core i5, Turbo Boost up to 3.6GHz 8GB RAM 1TB Fusion Drive NVIDIA GeForce GTX 680MX 2GB GDDR5 I am generally happy with the system. My only concern is that when I open certain programmes (mostly games) I get a moment of "scrambled" graphics i.e. choppy blocks of colour and static. It only lasts 1/2 a second or so. Is this an issue other people have encountered? Should I be concerned / ask for a replacement system?