DLP+TLP processors for the next generation of media workloads

Future media workloads will require about two levels of magnitude the performance achieved by current general purpose processors. High uni-threaded performance will be needed to accomplish real-time constraints together with huge computational throughput, as next generation of media workloads will be eminently multithreaded (MPEG-4/MPEG-7). In order to fulfil the challenge of providing both good uni-threaded performance and throughput, we propose to join the simultaneous multithreading execution paradigm (SMT) together with the ability to execute media-oriented streaming μ-SIMD instructions. This paper evaluates the performance of two different aggressive SMT processors: one with conventional μ-SIMD extensions (such as MMX) and one with longer streaming vector μ-SIMD extensions. We will show that future media workloads are, in fact, dominated by the scalar performance. The combination of SMT plus streaming vector μ-SIMD helps alleviate the performance bottleneck of the integer unit. SMT allows “hiding” vector execution underneath integer execution by overlapping the two types of computation, while the streaming vector μ-SIMD reduces the pressure on issue width and fetch bandwidth, and provides a powerful mechanism to tolerate latency that allows to implement smart decoupled cache hierarchies