Study On And Design Of High-Performance ALU

ALU (Arithmetic and Logic Unit) is one of the most important units in the microprocessors, of which speed, power dissipation and area have decisive effect on the performances of the whole microprocessor. It is of great value to study on designing the ALU with high speed, low power dissipation and small area in application and practice.The paper investigates the structure and class of the ALU, with emphasis on the analysis of the arithmetic of the shifter and the adder in the ALU. Based on this, the optimized scheme is developed with barrel shifter and the method of"look-ahead inside and skip outside"as the design method for the core adder in 32-bit ALU. The result shows that the overall performance of the ALU has been improved effectively by this scheme.On the basis of the optimized design scheme, the optimized design for the logic of the adder and the circuit of the net list is obtained. The logic transformation of the arithmetic for the adder has been accomplished, which can avoid the power consumption caused by unnecessary flip in the high-speed computing device; Optimized cells are designed on the transistor-level to reduce the number of the transistor of the whole ALU.The completed ALU is simulated with the HSPICE tool. The simulation result proves that the ALU designed in the paper is functionally correct. With the delay of the critical path being 1.32ns, the power dissipation 96.4 mw, and the number of the transistor of whole ALU 4972, the design achieves the goal of higher speed, low power dissipation and small area.