Socket S1 638 pins; is the CPU socket type used by AMD for their Turion 64, Athlon 64 Mobile and later Sempron processors, which debuted with the dual core Turion 64 X2 CPUs. It replaces the existing Socket 754 for laptops. Socket S1 includes support for dual-channel DDR2 SDRAM, dual-core mobile CPUs, and virtualization technology, to compete with the mobile Intel Core 2 processor series and the ATM Turion 64 X2 TL-66 2.3GHz is the fastest processor I found that fits the pin configuration, but I am not sure if it is the best per se. That depends on if you are looking at power consumption, speed, or some other factor.