We are currently re-designing a Data Center and production floor. We have 6513s at our Core with Sup720's and a 6500 sitting idle. We are also looking at deploying more 6500's or 4506's for edge switches. My question is this. Our 6509 is about 4 years old and our 6513'2 are about 2 years old. Are there different revisions of the 6500 that support differnt backplane speeds and fabric controllers or has the 6500 backplane remained unchanged since its inseption?