Chip Firm AMD has now formally announced the existence of its Athlon XP+ family and said that Arthur Andersen will audit the ratings to help re-assure consumers of their authenticity.The so-called "PR Ratings" compare the performance of AMD Athlons with Palomino cores against their own processors and are based on 35 different benchmarks, according to a representative at the launch of the chips in Milano today.That means there"s no easy way to transform, say a 2.2GHz Pentium 4 or a 2.4GHz Pentium 4"s clock speed into an AMD rating - more"s the pity.Responding to a question whether AMD would now be accused of confusing end users, a representative at the Milano press conference said poor performance from Intel Pentium 4 processors but fast clock speeds had forced his company to introduce the PR rating, because consumers would otherwise be dazzled by just the megahertz rating.