A computer system may determine a mode for a processor. The processor may support SMT, and it may have a first hardware thread with a first architected resource and a second hardware thread with a second architected resource. The computer system may determine that the processor is in a reduced-thread mode. The computer system may determine that the first hardware thread is a primary hardware thread that is active in the reduced-thread mode, and that the second hardware thread is a secondary hardware thread that is inactive in the reduced-thread mode. The computer system may disable the second hardware thread. The computer system may enable the first hardware thread to access the second architected resources.