1. A data processing system comprising: a processing unit including: a first LSU (load/store unit); a second LSU configured to operate independently of the first LSU in single and multi-thread modes; a first store buffer coupled to the first and second LSUs; and a second store buffer coupled to the first and second LSUs, wherein the first store buffer is used to execute a first thread in multi-thread mode, the second store buffer is used to execute a second thread in multi-thread mode, and the first and second store buffers are used when executing a single thread in single thread mode.