This is famous x86 CPU, it supports 1Mb address space. However, actual memory access is limited with 64Kb segments. This was criticized all the way, because using 1Mb space with so called HUGE memory model is slow. The other alternative is to use many 64Kb segments which is not that easy to handle. However, it's the price for being 16bit CPU and have access to 1Mb address space. This processor can run CP/M-86, MS-D0S and even Windows v3.0