I bought a new 27" ASUS PB278QR as an extra monitor for my iMac (27-inch, Mid 2011) with Thunderbolt. I had a Mini DisplayPort to DVI Adapter but when I use that, I only get 1920x1080 resolution and not the expected 2560x1440. I have now learned that this is due to the adapter only being Single Link DVI. Fair enough! I then bought an HDMI to Mini Display Port cable at Apple. That worked even worse. I'm not sure exactly what the resolution was. But the picture looked terrible. So I returned that cable. Then I bought a Mini-DisplayPort adapter cable. This did not work at all. When I plug it in, the monitor goes black, then occasionally shows a picture for half a second, then goes black again. There is also some nasty noise from the speakers. I called the store and they will send me another cable of the same type. I have yet to receive it. But I must say that I am doubtful. Does anybody have experience with connecting a 2560x1440 non-Tunderbolt monitor to a Thunderbolt Mac? What cable did you use?