because rootfs is located in 256mb chip that is integrated to the processor (not 110% sure) and opt is a part of 32gb flash chip. http://wiki.maemo.org/N900_filesystem http://wiki.maemo.org/Comparison_Table http://wiki.maemo.org/Nokia_N900 e: and of course 256mb could have been for example 2048 but I quess there would have been about similar leap to the device price...