The 8051 architecture has been loosely called a Harvard architecture for many years. Under the strictest terms I suppost it is not a true implementation since all the memory spaces share the same data / addr busses. But imagine why Intel did this in the first place. If they made a similar part to 8051 that had separate busses for everything the external interfaces would have required 2 8-bit data busses, two 16-bit address busses (or 8-bit multiplexed busses), and two sets of read/write/ALE lines. Quite impractical for the 40-pin DIP packages of the day.

For an interesting study of Harvard architecture parts you may want to also look at the old Signetics 8X300 processor. It was an impressive beast for its day!! Here is a link with some information: http://www.cpu-museum.com/8X300_e.htm. More is availilable via Google.

Michael Karas