Simultaneous multithreading (SMT) - Hardware organization (1)
SMT processors can be organized in two ways:
First: Instructions of different threads share all buffer resources in an extended superscalar pipeline
- Thus SMT adds minimal hardware complexity to conventional superscalars,
- hardware designers can focus on building a fast single-threaded superscalar and add multithread capability on top.
- Complexity added to superscalars by multithreading are thread tag for each internal instruction representation, multiple register sets, and the abilities of the fetch and the retire units to fetch respectively retire instructions of different threads.