Debugging Hardware Performance on Gen X Servers

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This post details the debugging process for performance discrepancies observed in Cloudflare's Gen X AMD EPYC Zen 2 (Rome) servers. The investigation involved using DGEMM to assess compute performance and TDP, comparing BIOS settings, running iPerf for network bottlenecks, and utilizing the AMD HSMP tool. The root cause identified was a mismatch between the memory clock frequency (1467 MHz) and the Infinity Fabric clock frequency (1333 MHz) on the underperforming SKU-B servers. A vendor-provided BIOS update that synchronized these frequencies to 1467 MHz resolved the performance gap.