Not only that but they would change the behavior of a chip between revisions, so drivers for one revision, if they didn't take into account the changes, would s

Not only that but they would change the behavior of a chip between revisions, so drivers for one revision, if they didn't take into account the changes, would suddenly stop working even though you bought the same ( but unknown to you, newer) version of the card. (source: me, who worked at a company that made commercial Linux drivers for Matrox, ATI,NeoMagic etc. chips )