Understanding Simultaneous Multithreading in Modern Processors

This lecture discusses the concept of simultaneous multithreading (SMT) and its implementation in modern processors. It begins by reviewing the evolution of processor architectures, focusing on dynamically-scheduled architectures and the challenges they face, such as dependency issues and wasted issue slots. The instructor explains the need for multithreading to enhance performance by allowing multiple threads to share execution resources. Different multithreading techniques, including cycle-by-cycle and block interleaving, are introduced, highlighting their advantages and drawbacks. The lecture emphasizes the importance of efficient thread scheduling and the architectural requirements for SMT, such as multiple program counters and register files. The instructor also addresses the impact of SMT on single-thread performance and the trade-offs involved. Finally, the lecture covers real-world implementations of SMT, particularly in Intel's hyper-threading technology, showcasing its benefits and the minimal additional costs associated with its integration. Overall, the lecture provides a comprehensive overview of SMT and its significance in advancing processor performance.