Power consumption in a microprocessor platform is managed by setting a peak power level for power consumed by a multi-core microprocessor platform executing multi-threaded applications. The multi-core microprocessor platform contains a plurality of physical cores, and each physical core is configurable into a plurality of logical cores. A simultaneous multithreading level in at least one physical core is adjusted by changing the number of logical cores on that physical core in response to a power consumption level of the multi-core microprocessor platform exceeding the peak power level. Performance and power data based on simultaneous multi-threading levels are used in selecting the physical core to be adjusted.