 Instruction address zero might identify a twenty-four-bit value, while data address zero might indicate an eight-bit byte that is not part of that twenty-four-bit value.A modified Harvard architecture machine is very much like a Harvard architecture machine, but it relaxes the strict separation between instruction and data while still letting the CPU concurrently access two (or more) memory buses.The most common modification includes separate instruction and data caches backed by a common address space.