Why can’t I set the frequency to 144Hz on my XL2411/XL2411P?

Please check the following:
1) Make sure your graphics card has a DVI port and a DVI Dual Link cable is used.
2) Make sure the BenQ bundled DVI cable is used.

Note: Only DVI Dual Link supports 144Hz on the XL2411.
Both DVI Dual Link and DisplayPort 1.2 support 144Hz on the XL2411P.