Here are the revised detailed instructions, with screenshots
1) Fire up ToastyX CRU. (get CRU here: http://www.monitortests.com/forum/Thread-Custom-Resolution-Utility-CRU
2) If you have more than one monitor, make sure you have the right one selected in the dropdown. Edit the existing detailed resolution, which should be 2560x1440x60. Then push the 'copy' button to copy the timings. Your numbers will be different from mine because I'm making the screenshots on a different kind of monitor.
3) If you have any established or standard resolutions, other than 640x480x60, you can go ahead and uncheck/delete them. Then add a new detailed resolution.
4) Paste the timings into the new resolution. Then, set the refresh rate to 120Hz (or 90Hz if you think your monitor can't do 120).
5) Edit the back porch to be a larger number. The target is 500, which I think is more likely to work at 90Hz. Still, I'm interested in knowing how good the results are at either refresh rate.
6) Click 'OK' to everything and reboot.
7) Use your video control panel to set your monitor to the new custom video mode and see how it goes.
8) Repeat steps 5-7 until you have "enough." At 90Hz, 500 back porch is about the same pixel clock as normal timings@120Hz. At 120Hz, this is very very fast. Feild Scarecrow reported 2000 total lines @120Hz (about the equivalent of a 550 back porch). You should probably increase by about 100 rows at a time if you are doing 120Hz, but at 90Hz you probably don't have to bother if you have already done 120Hz with ordinary timings.
Let us know how it goes, how many lines you reached, what video card and monitor (QNIX vs X-Star) you have and if your picture quality improved, got worse, or stayed the same. If your monitor freaks out, it's unlikely it will be damaged, but you might need to reboot to safe mode or have a second connected monitor to reset your settings.Edited by fluffysheap - 5/28/13 at 9:40pm