I was having trouble getting this to work but i finally nutted it out.Standard G-Sync Overclocking
When overclocking G-Sync on my XL2420G (Maybe all 1080p G-Sync monitors) there are only three things you have to look at, the Refreshrate, Total Horizontal Pixels and the Pixel Clock. The Front porch and Sync width can be what ever they like as long as they are low enough to not steal all the bandwidth and the Vertical Total HAS to be Active Vertical +18.
Now when adjusting the timings to get a new refreshrate you need the pixel clock to be BETWEEN
319.5 - 329.5
if it goes outside of any of these variables the monitor will simply black screen. So what you have to do is lower your Horizontal Total and raise your Refreshrate trying to stay BETWEEN those variables.http://i.imgur.com/F9RewNt.png
This alone i was able to get 153hz before frame skipping. I'm able to crack it to 198hz using this technique. http://imgur.com/HuMxPL1
I left the Vertical Timings 3 and 5 because G-Sync wasn't working correctly when they were left at 1. I don't understand why, but adjusting the Active Horizontal and Vertical didn't let me get any higher of a overclock, it would just frame skip at 154hz again.Unlocked Glitch State
Imagine what if we could adjust the Vertical Total and go WAY above the pixel clock. Well you can, sort of. To enter this 'Glitch' state you need a few things set in the timings.
The resolution NEEDS to be:
800 x 600 to 610
1024 x 768 to 778
And the Pixel clock need to be OUTSIDE of the standard Pixel clocks i mentioned earlier.
240 - 280
290 - 319.5
It will look something like this: http://imgur.com/xXeQBo8
I get 196hz before it craps out. Again i use 3 and 5 for G-Sync and i raised the Vertical total because there was a tearline going through my screen and raising by that much fixed it, it's dependent on the Refreshrate and the Active Pixels.
So i hope you found that interesting and wasn't too hard to follow! I really want to find more resolutions that work, i need one that's close to 1080.