Closer to 5x than 10x. Don't do the math based on the clock speed, look at the cycle times (which are mostly the same between DDR3 2000 and LPDDR2 533). A desktop or laptop CPU (unless by "laptop" you mean "netbook" -- laptops based on mainstream CPU cores have the same memory interconnect as desktops) will have two 64 bit DRAM channels, a typical phone will have a single 32 bit channel.