A system and process for managing thread transitions includes providing two data register sets coupled to a processor and using, by the processor, the two register sets as first-level registers for thread execution. A determination is made whether a quantity of the first-level registers needed to execute one or more threads exceeds a quantity of the first-level registers of the two data register sets. Responsive to determining that the quantity of the first-level registers needed to execute the one or more threads exceeds the quantity of the first-level registers of the two data register sets, a portion of main memory or cache memory is assigned as second-level registers where the second-level registers serve as registers of at least one of the two data register sets for executing the one or more threads.