An effective thermal management scheme, called active bank switching, for temperature control in the register file of a microprocessor is presented. The idea is to divide the physical register file into two equal-sized banks, and to alternate between the two banks when allocating new registers to the instruction operands. Experimental results show that this periodic active bank switching scheme achieves 3.4℃ of steady-state temperature reduction, with a mere 0.75% average performance penalty. Categories and Subject Descriptors B.7.2 [Hardware]: Design Aids General Terms: Design, Reliability Keywords Thermal model, Temperature-aware Design, Register File