The SNIC/KTH PRACE prototype: Achieving high energy efficiency with commodity technology without acceleration

Energy efficiency has become one of the most important considerations for HPC systems, particularly for large scale systems, for economic and environmental reasons and in exceptional cases also social and political. Many approaches are currently being pursued both in regards to architecture and hardware and software technologies to improve energy efficiency for HPC systems. The prototype described here, one of several within the PRACE project exploring improved energy efficiency, explores energy efficiency achievable through use of commodity components for cost effectiveness, and without acceleration for preservation/ease of portability of the large application code base that exists for the type of HPC systems that have been dominating for a decade. The prototype development was a collaborative effort between industry and academia. With a very limited budget for a server design project and severe time constraints the novelty was effectively limited to careful component choices in regards to energy efficiency for HPC workloads and a new motherboard design to support the component choices. A further constraint was that the outcome would be of production quality in order for the industry partners to market the prototype design should it be successful. For the component choices we did a characterization of the power consumption of a blade chassis and made an effort to measure the energy consumption of different memory modules under HPC workloads, information we could not find neither in the literature nor from memory or system vendors. Memory power consumption in the prototype, as well as most HPC systems, is second only to the CPU, sometimes a close second. We report on the design of the prototype, and preliminary performance results with an emphasis on the energy aspects of benchmarks and compare our results with the Blue Gene/P that, after its introduction, has dominated the top of the Green500 list for systems not using acceleration. The preliminary results show that energy efficiency comparable to the BG/P can be achieved without any proprietary technology at a fraction of the cost. The prototype design is now included in the standard product line of the participating platform vendor.