The branding of AMD's 64-bit CPUs. AMD was first to add 64-bit capability to the x86 architecture, with the introduction of the Opteron in 2003. Subsequent AMD64 lines include the Athlon and Phenom models for desktop computers and the low-power Turion line for laptops. Following AMD, Intel later added its own 64-bit architecture to the x86 family (see x64). Direct Connect Architecture The AMD64 design, known as the Direct Connect Architecture (DCA), includes a set of 64-bit instructions as well as 64-bit registers that allows the CPU to address more than 4GB of memory, which is the limit of 32-bit registers. It also added a DDR memory controller directly on the CPU chip for increased performance. See Opteron, Athlon, Sempron, Turion and AMD64 sockets.