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[Bug 92599] [NEW] Incorrect (low/stuttering) refresh rate with NVIDIA driver


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The problem here is that incorrect information from the NVIDIA driver is
tricking some software like Compiz into using an incorrect refresh rate,
which makes the whole desktop look choppy.

The cause of this framerate problem is the DynamicTwinView feature of
the NVIDIA graphics driver. It appears to be a documented "feature" of
the driver, and has been for several years:

--- Quote from the NVIDIA documentation ---
Option "DynamicTwinView" "boolean"
Enable or disable support for dynamically configuring TwinView on this X screen. When DynamicTwinView is enabled (the default), the refresh rate of a mode (reported through XF86VidMode or XRandR) does not correctly report the refresh rate, but instead is a unique number such that each MetaMode has a different value. This is to guarantee that MetaModes can be uniquely identified by XRandR.
When DynamicTwinView is disabled, the refresh rate reported through XRandR will be accurate, but NV-CONTROL clients such as nvidia-settings will not be able to dynamically manipulate the X screen's MetaModes. TwinView can still be configured from the X config file when DynamicTwinView is disabled.
Default: DynamicTwinView is enabled.
--- End quote ---


(in /etc/X11/xorg.conf)
Section "Device"
  Option "DynamicTwinView" "False"

If the workaround doesn't work for you and you still see
stuttering/jerkiness then you probably have bug 888039, which is caused
by other performance regressions in the Ubuntu 11.10 release.


Binary package hint: xorg

My Samsung SyncMaster 931BF does actually support 75 hz screen refresh
rate, but xorg lets me choose only between 50 Hz and 54 Hz. Modification
of /etc/X11/xorg.conf does not help. xorg worked ok on edgy.

Here's some info:

$ uname -a
Linux Xel-Naga 2.6.20-10-generic #2 SMP Mon Mar 12 00:02:49 UTC 2007 i686 GNU/Linux

$ apt-cache show xorg | grep Version
Version: 1:7.2-0ubuntu7

The video card is Nvidia GeForce 7300GS.

ProblemType: Bug
Architecture: i386
Date: Thu Mar 15 21:08:22 2007
DistroRelease: Ubuntu 7.04
Uname: Linux Xel-Naga 2.6.20-10-generic #2 SMP Mon Mar 12 00:02:49 UTC 2007 i686 GNU/Linux

** Affects: nvidia-drivers-ubuntu
     Importance: Undecided
         Status: Confirmed

** Affects: compiz (Ubuntu)
     Importance: Undecided
     Assignee: Daniel van Vugt (vanvugt)
         Status: In Progress

** Affects: nvidia-graphics-drivers (Ubuntu)
     Importance: Wishlist
         Status: Confirmed

Incorrect (low/stuttering) refresh rate with NVIDIA driver
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