diff -ur glxgears.orig/glxgears.c glxgears/glxgears.c
--- glxgears.orig/glxgears.c	2005-04-15 10:37:23.000000000 +0200
+++ glxgears/glxgears.c	2009-01-20 17:57:12.000000000 +0100
@@ -42,6 +42,7 @@
  *
  */
 
+#define _GNU_SOURCE
 
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
@@ -862,6 +863,14 @@
       printf("GL_EXTENSIONS = %s\n", (char *) glGetString(GL_EXTENSIONS));
    }
 
+   if (! glXIsDirect(dpy, ctx))
+       printf ("\n***\n*** WARNING: Direct Rendering is NOT enabled\n***\n");
+   else if (strcasestr ((char *) glGetString(GL_RENDERER), "software"))
+       printf ("\n***\n*** WARNING: Hardware acceleration is NOT active\n***\n");
+   printf ("\n*** NOTE: Don't use glxgears as a benchmark.\n"
+	   "    OpenGL implementations are not optimized for frame rates >> 60fps,\n"
+	   "    thus these numbers are meaningless when compared between vendors.\n\n");
+
    init();
 
 #ifdef BUILD_PRINTSUPPORT