Core Duo Yonah processors were used at first, clocked at 1.83 (T2400), 2.0GHz (T2500) and 2.16GHz (T2600). For memory, they used 667MHz PC-5300 DDR2 SO-DIMM SDRAM right up to late 2008 models. Core Duos unfortunately were 32bit only processors, thus limiting the maximum memory capacity to 2GB or 4GB (3GB usable),