Specifications for a variable-precision arithmetic coprocessor

The authors have been developing a programming system intended to be especially convenient for scientific computing. Its main features are variable precision (decimal) floating-point arithmetic and convenient exception handling. The software implementation of the system has evolved over a number of years, and a partial hardware implementation of the arithmetic itself was constructed and used during the early stages of the project. Based on this experience, the authors have developed a set of specifications for an arithmetic coprocessor to support such a system. These specifications are described. An outline of the language features and how they can be used is also provided, to help justify the particular choice of coprocessor specifications. The authors also indicate what other hardware features would be most helpful to the systems programmer, especially for implementation of the exception handling.<>