1. An x87 fused multiply-add (FMA) instruction for storage in a computer system memory and for execution by an x86 architecture microprocessor having an x87 floating-point unit (FPU) register stack, comprising: first and second operands, implicitly specified as stored in first and second registers of the register stack, said first and second registers being the top two registers of the register stack; and a third operand, explicitly specified in the instruction as stored in a third register of the register stack; wherein the FMA instruction instructs the microprocessor to multiply said first and second operands to generate a product, and to add said third operand to said product to generate a result.