This dissertation presents the results of the research, design, and implementations of several new architectures for floating-point fused multiplier-adders used in the x87 units of microprocessors. These new architectures have been designed to provide solutions to the implementation problems found in modern-day fused multiply-add units. The new three-path fused multiply-add architecture shows a 12% reduction in latency and a 15% reduction in power as compared to a classic fused multiplier-adder. The new bridge fused multiply-add architecture presents a design capable of full performance floating-point addition and floating-point multiplication instructions while still providing the functionality and performance gain of a classic fused multiplier-adder. Each new architecture presented as well as a collection of modern floating-point arithmetic units that are used for comparison have been designed and implemented using the Advanced Micro Devices (AMD) 65 nanometer silicon on insulator transistor technology and circuit design toolset. All designs use the AMD ‘Barcelona’ native quadcore standard-cell library as an architectural building block to create and contrast the new architectures in a cutting-edge and realistic industrial technology.