Implementing microprocessors from simplified descriptions

Despite the proliferation of high-level synthesis tools, hardware description of microprocessors remains complex. We argue that much of the incidental complexity can be relieved by untangling the description into separate functional and microarchitectural components. Such an untangling can be achieved using a high-level microcode compiler that can generate not only microcode, but also the micro-instruction format and the interpretations of each control bit. Simplifying hardware description will help the designer make better design-space trade-offs, and close the design and verification loop faster. This paper takes the reader through an implementation of a simple Y86 processor to qualitatively illustrate the complexity reduction from the untangling.