So? Copying a megabyte is a really expensive thing to do inside a loop, even ignoring caches. (A full speed memcpy would take 40 microseconds, based on a memory

So? Copying a megabyte is a really expensive thing to do inside a loop, even ignoring caches. (A full speed memcpy would take 40 microseconds, based on a memory bandwidth of 24 GB/s, which is a long time.)