CPU-Only Compute Still Matters To A Lot Of HPC Centers

Why It Matters

The enhanced memory bandwidth and predictable cache behavior give HPC centers a viable, cost‑effective alternative to buying hardware, accelerating the shift to cloud‑based simulation workloads. This move also pressures competitors to improve CPU‑only offerings and network adapters.

Key Takeaways

• AWS HPC8a uses AMD Turin EPYC 9R15 processors.
• Memory bandwidth up to 40% higher than Genoa-based HPC7a.
• SMT disabled for predictable cache latency in MPI workloads.
• 300 Gb/s EFA‑2 network unchanged; no EFA‑3 yet.
• Fixed 96‑core, 768 GB configuration limits flexibility.

Pulse Analysis

Cloud‑based high‑performance computing has finally caught up with legacy on‑premise clusters, largely because many scientific codes remain CPU‑centric. AWS’s HPC8a instances illustrate this trend, offering a fully tuned CPU‑only environment that leverages AMD’s Turin EPYC 9R15 silicon. By providing two‑socket, 192‑core machines without simultaneous multithreading, the instances deliver deterministic cache performance—crucial for MPI‑driven workloads that dominate simulation and modeling tasks.

The technical edge of the HPC8a lies in its memory subsystem. Turin chips expose twelve memory controllers per socket and pair with faster DDR5 modules, delivering up to a 40 % uplift in memory‑bandwidth‑constrained scenarios compared with the earlier Genoa‑based HPC7a. Although peak FP64 floating‑point throughput remains similar, the real‑world speedup stems from reduced latency and higher bandwidth, translating into a quoted 25 % price‑performance advantage. AWS’s pricing model, which keeps on‑demand rates steady across core configurations, further simplifies budgeting for research institutions.

Despite these gains, the network layer remains a bottleneck; both HPC7a and HPC8a rely on 300 Gb/s EFA‑2 adapters, and an EFA‑3 offering has yet to materialize. Additionally, the current “fat” configuration—96 cores paired with 768 GB memory—limits flexibility for workloads that require different core‑to‑memory ratios. As cloud providers continue to refine CPU‑only HPC services, customers should weigh memory bandwidth benefits against network constraints and consider managed Lustre storage options to maximize throughput in virtual clusters.