Comment 8 for bug 334141

You can't really use top output as a remotely reliable source of memory information. Even to get the numbers I posted above, I was pulling those out of /proc/$PID/status and I don't think that's really a completely accurate source of memory information. To get realistic numbers you probably need to use something like valgrind.

If you don't know what type of video card/driver you're using, you might be able to give Mirco an estimate with the GLX renderer string. Try running:
   glxinfo | grep renderer

For example, on my Intel X3100 it says:
   OpenGL renderer string: Mesa DRI Intel(R) 965GM GEM 20090114 x86/MMX/SSE2

Maybe there's a way to get a more accurate description of your video hardware, I don't know.