@tnt's
yeah, if they don't have texture compresssion they'll run with "32bit textures" instead. although this is a performance disadvantge for those cards, they will still be blocked.
@aquamark
i don't think so. i mean who knows all specs of the cards and knows that they don't support that? there's no clue like "the benchmark wasn't run on default" from 3dmark01 in aquamark.