Apparatus to perform Newton iterations for reciprocal and reciprocal square root

A multiplier for performing reciprocal and reciprocal square root computations of a value C using iterative numerical techniques, the multiplier having XS input and an XR input respectively, the XS and XR inputs having variable values dependent upon which iteration the multiplier is processing, said variable values including the value C, x.sub.m, and p.sub.m, wherein x.sub.m is an mth iteration of a function F(x) wherein said F(x) approximates 1 divided by the value of C, and wherein the p.sub.m is equal to a product of the value C and the x.sub.m, the multiplier comprising:

• a mantissa processing portion having;
• a) an XS mantissa operand format block having an input port for receiving the XS input, said XS mantissa operand format block normalizing the XS input to create an XS mantissa operand;
• b) an XR mantissa operand format block having an input port for receiving the XR input, said XR mantissa operand format block normalizing the XR input to create an XR mantissa operand;
• c) an accumulator format block for receiving the XR input and for correctly compensating the XR input by placing the XR input in a correct position for further computations thereby creating an XR formatted operand;
• d) control circuitry for determining a selected case of a first case and a second case of which said XS and XR inputs are representative and for generating a control signal according to a generated opcode containing a mnemonic for a function to be performed specific to said selected case, said control signal being an input to said XS mantissa operand format block, said XR operand format block, and said accumulator format block thereby allowing said opcode to be implemented on the XS and XR inputs in said XS mantissa operand format block, said XR operand format block, and said accumulator format block, said opcode thereby determining said normalization and said correct position appropriate to the XS and XR inputs;
• and
• e) a fixed point multiplier-accumulator for receiving said normalized XR and XR mantissa operands and said XR formatted operand, said fixed point multiplier-accumulator performing a first stage computation by forming a product of said normalized XR and XS mantissa operands and then adding said XR formatted operand to said product, said first stage computation representing a fixed point product of said reciprocal and said reciprocal square root of the value C.