Hardware/Software trade-offs: Hardware Design Viewpoint

The purpose of this paper is to discuss the concept of hardware/software trade-offs from the perspective of the hardware designer. Primarily, the paper will examine software oriented functions/goals/requirements and discuss considerations in determining the kind of hardware support which would be involved in implementing the particular concept. This orientation follows a long-standing tradition; i.e., traditionally what appears in hardware is a result of functions which migrated into software packages, as the overall user community recognized their usefulness, and eventually migrating into hardware/firmware as manufacturers realized the usefulness of the functions. There are three dimensions to usefulness; i.e., is the function well understood, broadly used, and is the function cost effective to implement in hardware. Examples of functions which migrate from software into hardware are: floating point arithmetic, indexing, and memory management systems (virtual memory). A classic example of a function (well understood and broadly used) which has not migrated into hardware is payroll accounting. Probably the most important point is that payroll accounting routines are very specialized and many different versions (some observers place the number around 50,000) exist so that there is little standardization. This, however, does not preclude the placing of payroll accounting or other complex functions into hardware. For example, a number of researchers are currently seriously pursuing the problem of providing hardware support for data base management systems.