Two upcoming ultra low voltage Intel CPUs will end up branded as Core i7 640UM and 620UM. The 6x0 series remains reserved for Core i7 dual-core Arrandale in Calpella platform, while the 5x0 designation will be reserved for Core i5 series that has 3MB of cache.
Core i7 620UM has 4MB of cache and that is the only major difference between this CPU and Core i5 520UM.However, Core i7 series will overclock better in Turbo and you can expect that 1.06GHz Core i7 620UM overoclocks to a whopping 2.13GHz when pluggged in or running at full performance settings, and all of this can be sustained with an 18W TDP.
Core i7 640UM will have the base clock of 1.2GHz and with the help of Turbo it will overclock all the way to 2.26GHz. The 620UM will sell for $278 while 640UM will end up at an acceptable $305. Both of them will most probably become a synonym for great performance.