Soft Core Processor Design

I have been wanting to build a processor from scratch for a while now. I really enjoy building up complex structures from first principles. I find it is the best way to understand how they work. I had a really great opportunity to design all the fundamental cells for digital design in a class I took on VLSI. In a couple projects we designed a standard library of cells composed of inverters, AND gates, OR gates, and D Flip Flops. We had to design the transistor circuits, simulate our design, and layout our circuits. We then used the library to synthesize a small state machine that we designed on SystemVerilog. Good stuff. Designing a processor seems like the next logical step. I already have a good understanding of all the core components that make up a processor. What I am hoping to understand better is the coordination between all the components.

However, just like with any good project, before I can start the fun stuff I need to do some planning. Planning in this case means requirements. Because this project is self imposed my requirements going to more resemble goals or things I think would be neat. There are, however, some basics I would like to start with.

The main distinction to be made between harvard architecture and von Neumann is the separation of address spaces. With the von Neumann architecture each memory address uniquely identifies a storage location. This means instructions and data occupy the same address space. With the harvard architecture storage locations are not unique to a memory address. THis means that instructions and data must be in separate address spaces and you have to know which space the given address belongs.