Machine method to perform newton iterations for reciprocal square roots

A method for performing, in a processor, a reciprocal square root computation of a value C using iterative numerical techniques, the processor having an XS input and an XR input, the method comprising:

• a) determining in input select circuitry, a value of said XS input and a value of said XR input, said XS and SR input values being a function of an iteration being processed;
• b) determining in control circuitry a selected case of a first case and a second case;
• c) generating a control signal, in said control circuitry, according to a generated opcode containing a mnemonic for a function to be performed specific to said selected case;
• d) normalizing the XS input in an XS mantissa operand format block according to said control signal to provide a normalized XS mantissa operand;
• e) normalizing the XR input in an XR mantissa operand format block according to said control signal to provide a normalized XR mantissa operand;
• f) compensating the XR input in an accumulator format block according to said control signal to create an XR formatted operand;
• and
• g) 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, a result of said first stage computation representing a fixed point product of the reciprocal square root computation of the value C.