Floating-point processor with operating mode having improved accuracy and high performance

摘要

Floating-point units (FPUs) and processors having a "flush-to-nearest" operating mode that provides improved accuracy over a conventional "flush-to-zero" mode. The FPU or processor includes an operand processing section and an operand flush section. For each floating-point operation, the operand processing section receives and processes one or more input operands to provide a preliminary result. The operand flush section determines whether the preliminary result falls within one of a number of ranges of values and sets the preliminary result to one of a number of set values if the preliminary result falls within one of the ranges. In a specific implementation, a first range of values is defined to include values greater than zero and less than half of a minimum normalized number (i.e., 0<|Y|<+A_min/2), a second range of values is defined to include values equal to or greater than +a_min/2 and less than +a_{min, (i.e., amin/2<=|Y|min}), and the preliminary result is set to zero if it falls within the first range and to +a_min or -a_min (depending on the sign bit) if it falls within the second range.