One of the key selling points of Opteron is investment protection. Makers of AMD systems have only needed to qualify two platforms between the years 2003 and 2009.
AMD platforms accompany memory technologies–DDR, DDR2, DDR3, that sort of thing–thanks to the company integrating the memory controller on-die.
Ironically, AMD would never transition to a new memory technology if it were not for other companies pushing the envelope of technology and supporting new memory technologies many years in advance of the memory going mainstream.
AMD Technology Analyst Day