Machine method to perform newton iterations for reciprocals

A method for performing a reciprocal computation of a value C using iterative numerical techniques in a multiplier, the multiplier having an SX 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 value of C, and wherein the p.sub.m is equal to a product of the value C and the x.sub.m, the method comprising:

• a) determining in control circuitry a selected case of a first case and a second case of which said XS and XR inputs are representative;
• b) generating a control signal in said control circuitry, said control signal having a generated opcode containing a mnemonic for a function to be performed specific to said selected case;
• c) normalizing the XS input in an SX mantissa operand format block by implementing said function specific to said opcode generated by said control circuitry to provide a normalized XS mantissa operand;
• d) normalizing the XR input in an XR mantissa operand format block by implementing said function specific to said opcode generated by said control circuitry to provide a normalized XR mantissa operand;
• e) compensating the XR input in an accumulator format block by implementing said function specific to said opcode generated by said control circuitry to create an XR formatted operand, said compensating providing correct positioning of the XR input for future computations;
• and
• f) performing a first stage computation in a fixed point multiplier-accumulator 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 the reciprocal computation of the value C.