I will teach you the steps to create a ~21:9 (actual 64:27) ultra wide resolution on native 16:9 display
What are the advantages of this?
To test what ultrawide feels like.
To lower the resolution on a native 4k display for higher FPS.
To maintain 1:1 pixel mapping.
Fun Fact: A 40" 4k display ran as an ultrawide will have a higher resolution and a larger screen than an actual 34" 3440*1440 ultrawide display.
Step 1) Open NVIDIA Control Panel and click "Customize..."

Step 2) Check box "Enable resolutions not exposed by the display"

Step 3) Click "Create Custom Resolution"

Use following resolutions
4k Ultrawide: 3840x1620
1440p Ultrawide: 2560x1080
1080p Ultrawide: 1920x810
Step 4) Aspect Ratio should be set to either "Aspect Ratio" or "No Scaling."

Credits: Pics from http://forums.guru3d.com/showthread.php?t=346325
What are the advantages of this?
To test what ultrawide feels like.
To lower the resolution on a native 4k display for higher FPS.
To maintain 1:1 pixel mapping.
Fun Fact: A 40" 4k display ran as an ultrawide will have a higher resolution and a larger screen than an actual 34" 3440*1440 ultrawide display.
Step 1) Open NVIDIA Control Panel and click "Customize..."
Step 2) Check box "Enable resolutions not exposed by the display"
Step 3) Click "Create Custom Resolution"
Use following resolutions
4k Ultrawide: 3840x1620
1440p Ultrawide: 2560x1080
1080p Ultrawide: 1920x810
Step 4) Aspect Ratio should be set to either "Aspect Ratio" or "No Scaling."
Credits: Pics from http://forums.guru3d.com/showthread.php?t=346325