Architecture Generator for Type-3 Unum Posit Adder/Subtractor

Abstract

This paper is aimed towards the hardware architecture aspect of a recently proposed posit number system under type-3 unum (universal number system). Here, an algorithmic flow for the posit addition/subtraction arithmetic is developed and its hardware architecture is designed. Compare to floating point, posit provides better dynamic range and accuracy over same word size, along with more accurate and exact arithmetic support. Posit format includes a run-time varying exponent component, provided by a combination of regime-bits (of run-time varying length) and exponent-bits (of size up to ES bits). Thus, the mantissa precision also varies at run-time. This provides a combination of dynamic range and precision under a given word size (N). This possible variation in format along dynamic range and precision may attract various applications with different(accuracy and dynamic range) requirement. However, this run-time variation in posit format also poses a hardware design challenge. So, this paper is aimed towards the construction of an open-source parameterized Verilog HDL (Hardware Description Language) generator for posit adder/subtractor arithmetic, with parameterized N and ES.