# Environment Variables

Mesa supports the following environment variables:

- MESA_NO_ASM - if set, disables all assembly language optimizations
- MESA_NO_MMX - if set, disables Intel MMX optimizations
- MESA_NO_3DNOW - if set, disables AMD 3DNow! optimizations
- MESA_NO_SSE - if set, disables Intel SSE optimizations
- MESA_DEBUG - if set, error messages are printed to stderr. If value is "FP" abort upon floating point exceptions.
- MESA_NO_DITHER - if set, disables dithering, overriding glEnable(GL_DITHER)

The following environment variables are only applicable to the Xlib/X11 software driver:

- MESA_RGB_VISUAL - specifies the X visual and depth for RGB mode (X only)
- MESA_CI_VISUAL - specifies the X visual and depth for CI mode (X only)
- MESA_BACK_BUFFER - specifies how to implement the back color buffer (X only)
- MESA_GAMMA - gamma correction coefficients (X only)
- MESA_XSYNC - enable synchronous X behavior (for X debugging only)
- MESA_GLX_FORCE_CI - if set, force GLX to treak 8bpp visuals as CI visuals
- MESA_GLX_FX - set to either "fullscreen" for full-screen rendering, "window" to render into a window, or "disable" to disable the Glide driver.