To switch back to the General Timing Formula (GTF)
From the NVIDIA Control Panel navigation tree pane, under Display, click Change resolution.
Click the image that represents the display you want to affect.
Click Customize, then from the Customize dialog box, click Create Custom Resolution.
(Quadro and NVS products only) In the Select displays section of the Create Custom Resolution dialog box, select any additional connected displays to which you want to apply the change.
Click the Timing Standard list arrow and select GTF.
General Timing Formula (GTF) is an older but widely used timing standard. However, newer displays are switching to the CVT standard.
Click Test, then if the test passes and you want to save the new mode, click Save.