Try designing the format keeing the required features in mind and you might seen why they have.
The hardware has to be able to read and write data from an arbitrary location and do some kind of checksum for error detection and they have to be able to efficiently transfer this data to the cpu.
The hardware has to be able to read and write data from an arbitrary location and do some kind of checksum for error detection and they have to be able to efficiently transfer this data to the cpu.