Under Snow Leopard, 10.6.8, my new Dell U2713H doesn't come on when I Start Up my Mac Pro. I have to turn it off from energy saving mode, and back on. I also miss the spinning starting up window completely. Wonder what I would do if I needed to see a verbose startup.
It displays a message saying I need to correct the 2560x1440 @ 60Hz selection. I believe it selects the proper high resolution and frequency ... but to have to turn the monitor off / on isn't right.
I'm using the Dual DVI-D connector supplied by Dell with my Mac Pro ATI Radeon HD 2600, which has 2 dual DVI ports.
It works under 10.9.1 Mavericks ... and I also get full 2560 x 1440 @ 60Hz.