When the 8088/8086 came out, Harvard was still a major contender in minicomputer markets. The 8088 supports a Harvard configuration directly by outputting on s3 and s4 (pins 37 and 38) the segment register used to generate the address. This can, in a Harvard configuration be used to extend the memory space to 4MB by addressing 4 separate memory banks. Typically in embedded designs I have built or worked on, CS will refer to the firmware, SS to fast RAM, DS to NVRAM, and ES is generally used for primitive memory mapped IO. This trick does not work with modern processors int eh 8088 family due to the way caches keep track of memory locations.