How to switch videocard drivers

I have NVIDIA 9600 GT GPU and integreted Intel GMA 3100. Wanted to switch to GMA 3100
and as I do not know how to switch drivers I decided to remove NVIDIA GPU driver to
activate Intel driver (as I do this previously, in 12.3) but there was a problem: can not use neither the one nor the other. I tried to install both, NVIDIA & Intel, drivers but now no one is working.

Error message in /var/log/Xorg.0.log:
42.459] (EE) Failed to initialize GLX extension (Compatible NVIDIA X driver not found)

When I am trying to execute glxgears command I am receiving this message:
Xlib: extension “GLX” missing on display “:0”.
Error: couldn’t get an RGB, Double-buffered visual

I think driver should be loaded automatically, depending on the current device.

In Mageia I just switched videocard and all was fine.

You still have parts of the nvidia driver on your system. (it replaces libglx and libGL with its own incompatible versions)

How did you install it and how did you uninstall it?

I used zypper rm & zypper in. But there must be some way without uninstalling driver.

Yes, “zypper rm”.
But as I don’t know which nvidia packages you installed, I cannot tell you the exact command.

Maybe better run YaST->Software Management, type “nvidia” into the search field and uninstall all packages with “nvidia” in the name.

There is one more problem (I forget about this): when removing currently installed NVIDIA drivers system tells me that another version of NVIDIA driver (for older models of NVIDIA videocards) must be installed. I blacklisted this driver and all related packages and only after this Intel driver starts working.

And I know how to use zypper, so I do not need “exact command”.

And which package(s) did you remove exactly?
If you only remove the kmp f.e., another one will be installed to satisfy the dependencies. x11-video-nvidia-G0X f.e. requires one kmp-package to be installed (but doesn’t specify precisely which one, as it should work with all kernel flavors).

OTOH, the older (G02 I suppose?) driver might get installed, because it also supports your card. You could try to use the --no-recommends switch for zypper, or set “solver.onlyRequires = true” in /etc/zypp/zypp.conf.

Or remove/disable the nvidia repo, then the driver won’t be installed automatically any more as well, of course.

To have both the nvidia and the intel driver, you would have to use Bumblebee I suppose.
As I indicated already, the nvidia driver replaces some system libraries (libglx and libGL) with its own versions, which breaks the intel driver.
Bumblebee works around this.
With Bumblebee your system normally uses the intel chip, but you can run specific programs on the nvidia.

But if you want to use that, you should disable/remove the nvidia repo anyway.