Comment 18 for bug 157623

Following the information posted in the 2 forum links I posted above:

The DynmaicTwinView option defaults to ON as of nvidia driver 96xx and newer.

The effect of DynamicTwinView is (detailed in the driver README) such that the refresh rates are reported incorrectly as id numbers instead of hz values.

This works ok if you use the nvidia-settings application which is designed to get the actual hz values from the driver.

If DynamicTwinView is enabled, other then ids as hz values, the driver can support connecting say a TV dynamically and setup it's refresh rate separate from the other screen, through what it calls "metamodes", for details, the README of the driver is freely available.

In the first forum link I specified, Nvidia technicians have posted saying that this is the default behaviour and will not be changed.

So either Ubuntu's display settings pop-up continues to display incorrect hz values, which is fine, since these are closed source drivers (which I know are unsupported.)

On the other hand, if you want to enable desktop effects, you have to use the drivers.
If you then go to Screen Resolution or Screens and Graphics, your refresh rates are incorrect.

Perhaps if the user is already using the restricted drivers, we could also have a link to the nvidia-settings on the menu?

I don't know what is the best solution to this? perhaps doing nothing?

As far as how wide spread the issue is...
1. Only effects nvidia graphics card users
2. Only effects a subset of those users that want desktop-effects, or 3d support.
3. Only effects a subset of those users that don't edit their xorg.conf and use the default of DynamicTwinView ON
4. Only effects a subset of those users that use displayconfig-gtk or gnome-display-properties to change their refresh rate.

So, it will effect anyone that uses the restricted drivers manager to install nvidia, does not edit their xorg.conf, and goes to change their refresh rate using displayconfig-gtk or gnome-display-properties.

So using ballpark figures... (probably wildly incorrect)
if 30% of users use Nvidia chipsets
and 50% of those use restricted drivers to install nvidia for effects, or 3d
and 25% of those want to change their refresh rate
and 50% of those notice that 51hz does not look right
then about 2% of users will be effected.

Sorry for the long winded answer, but it's a complex issue...