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The original was posted on /r/hardware by /u/Pristine-Woodpecker on 2024-08-21 21:52:54+00:00.

This is hidden somewhere deep within the comments on the Chips and Cheese Zen 5 review. The Phoronix benchmarks with PostgreSQL 16 parallel read/write indeed show catastrophic scaling on Zen 5, with the 9950X performing slightly worse than the 5950X. This would indeed be the kind of parallel benchmark that needs continuous cross-CCX synchronization.

However, the same benchmark shows the 9900X performing as expected! Most of the other reviews that looked at the bad inter-CCX latency only tested the 9950X. So is this a benchmark oddity, or does it really only affect the 16-core variant?

The read-only tests, which would have less inter-CCX synchronization traffic, scale as expected on both chips.