if i remember it correctly the main difference of the "harvard"-architecture was: it uses its own data and program/instruction buses ...
* https://en.wikipedia.org/wiki/Harvard_architecture
i think texas instruments 320x0 signal-processors used this architecture ... back in, you guessed it!, the 1980ties.
* https://en.wikipedia.org/wiki/TMS320
ah, they use a modified harvard architecture :))
* https://en.wikipedia.org/wiki/Modified_Harvard_architecture
cheers!