A system and process for managing thread transitions includes determining that a transition is to be made regarding the relative use of two data register sets where the two data register sets are used by a processor as first-level registers for thread execution. Based on the transition determination, a determination is made whether to move thread data in at least one of the first-level registers to second-level registers. Responsive to determining to move the thread data, a portion of main memory or cache memory is assigned as the second-level registers where the second-level registers serve as registers of at least one of the two data register sets for executing a thread. The thread data from the at least one first-level register is moved to the second-level registers based on the move determination.