Volume 4, part 1 of the Ivybridge PRM says, "Generally, the EWA approximation algorithm results in higher image quality than the legacy algorithm." Using a classic anisotropic filtering "tunnel" demo, it appears that there is *no* anisotropic filtering on IVB without this bit set.
f74cf5f i965: Enable EWA anisotropic filtering algorithm
src/mesa/drivers/dri/i965/gen7_sampler_state.c | 1 +
1 file changed, 1 insertion(+)