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jeffbee10/12/20243 repliesview on HN

The part with only 16 cores but 512MB L3 cache ... that must be for some specific workload.


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phonon10/12/2024

Oracle can charge $40-$100k+ for EE including options per core (times .5)...and some workloads are very cache sensitive. So a high cache, high bandwidth, high frequency, high memory capacity 16 core CPU[1] (x2 socket) might be the best bang for their buck for that million dollar+ license.

[1] https://www.amd.com/en/products/processors/server/epyc/9005-...

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jsheard10/12/2024

The topology of that part is wild, it's physically the same silicon as the 128-core part but they've disabled all but one core on each compute chiplet. 112 cores are switched off to leave just 16 cores with as much cache as possible.

Inter-core latency will be rough since you'll always be hitting the relatively slow inter-chiplet bus, though.

addaon10/12/2024

Does anyone know if modern AMD chips allow mapping the L3 cache and using it as TCM instead of cache? I know older non-X86 processors supported this (and often booted into that mode so that the memory controllers could be brought up), but not sure if it's possible today. If so, that would sure make for some interesting embedded use cases for a large DRAM-less system...

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