If you have a picture when on P96 test mode you quickly see what happens if you alter the settings. By adjusting the clock (pixel clock or whatever it is) you get your vertical refresh into something your monitor can handle. As you see the working bands are narrow, maybe just a couple of Hz. I had my screenmode settings after a CRT tube hovering between 80 and 120 Hz refresh and had to lower the pixel clock lots and change some doublescan/normal/interlaced settings too to change everything into 60 (well, 59-61 accepted).