No stereoscopic pixelformat when monoscopic OpenGL application is already running.
This is a known problem and already fixed in the Windows NT 4.0 driver for GLoria-XL with a build number of ...348 and above. These drivers will be available soon.
Explanation:
If a non-stereoscopic OpenGL application is started, the video RAM will be organized by the driver in a way that double buffered OpenGL gets best performance.
After that the buffer layout is not changeable as long as any non-stereoscopic OpenGL application is running. That means at that time the different buffer layout needed for stereoscopic display (front_left, front_right, back_left, back_right color buffers) cannot be applied. Therefore no stereoscopic pixelformats are exported by the driver as long as a monoscopic one is started first.
If a stereoscopic OpenGL application sets its pixelformat first, then the buffers are configurated to get the four needed color buffers (if enough memory is available at that resolution, otherwise there won't be stereoscopic pixelformats at all). After that all additional OpenGL applications can get either stereo or monoscopic pixelformats. The content of monoscopic contexts will be drawn in both left and right buffers simultaneously.
ELSA GLoria-XL drivers with build number ....0348 and above fix this problem with the "Application Settings" panel in the display property page. Enable the "Stereo" switch to force a buffer layout suitable for stereocopic OpenGL applications.