Tibidabo1: Making the case for an ARM-based HPC system

• We build the first large-scale cluster with ARM processors.
• Existing HPC applications scale well without any tuning.
• We present valuable lessons that we learned while working on the prototype.
• We give directions for improving energy efficiency of HPC clusters with mobile CPUs.
• HPC systems with 16-core Cortex-A15 could reach 1046 MFLOPS/W.

It is widely accepted that future HPC systems will be limited by their power consumption. Current HPC systems are built from commodity server processors, designed over years to achieve maximum performance, with energy efficiency being an after-thought. In this paper we advocate a different approach: building HPC systems from low-power embedded and mobile technology parts, over time designed for maximum energy efficiency, which now show promise for competitive performance.We introduce the architecture of Tibidabo, the first large-scale HPC cluster built from ARM multicore chips, and a detailed performance and energy efficiency evaluation. We present the lessons learned for the design and improvement in energy efficiency of future HPC systems based on such low-power cores. Based on our experience with the prototype, we perform simulations to show that a theoretical cluster of 16-core ARM Cortex-A15 chips would increase the energy efficiency of our cluster by 8.7×, reaching an energy efficiency of 1046 MFLOPS/W.