I assume you mean what used to be called minicomputers. There was a time when they formed a fairly distinct group between desktop and mainframe computers, and included workstations and small analytical and control computers - remember the PDP8 series? But with time the boundaries disappeared, and the term tends to be used for smaller mainframe-type computers built mostly for specific applications. So there is no standard design, just a mass of proprietary products.
As a matter of interest, what was the aim of your project?