A CPU has an upper compatibility with a low-order CPU to expand a continuously usable address space relatively. For latching data information, registers are constructed for being an address register with a bit number larger than the address bit number of a low-order CPU. The data information has its...http://www.google.com/patents/US5666510?utm_source=gb-gplus-sharePatent US5666510 - Data processing device having an expandable address space
