2560x1440 Leo">
2560x1440 Leo"> ===> https://conttooperting.blogspot.com/?l=2tCZyY
I had this problem myself, and it was indeed due to not using a DVI dual link cable. And on top of that, the first videocard I tried on didn't support the resolution 2560x1440, but that was at work just to test. At home, I thought to make it quick and just replaced my monitor, and kept the cable I was using for years.
I've connected 27" Dell U2715H to MacBook pro 2012 and have a default resolution 2560x1440. It looks nice but the font size is waaaay too small, so I had to lose some of this niceness by scaling down to 2048x1152. 781b155fdc