XL series are our only models that are capable of high refresh rate (120,144).
Few things to check.
1. Make sure you’re using a DL-DVI (Dual link DVI) cable or a Display port cable (DP). An adapter can be used, but the source must be DL-DVI, Display port, or mini DisplayPort.
2. Confirm your graphics can support high refresh rate.
3. If using DL-DVI, make sure it is plugged into the DL-DVI input in your graphics card because the DL-DVI also fits into the single link DVI input.
4. Set your refresh rate in your graphics card settings by right clicking desk top -> screen resolution -> advanced settings -> monitor tab -> selecting refresh rate in the drop down box.