I haven't touched a 7900X, but AMD Rome and Milan have core complex (CCX) that share 16MB L3 cache. AMD Rome has significantly faster L3 cache than Intel (https

I haven't touched a 7900X, but AMD Rome and Milan have core complex (CCX) that share 16MB L3 cache. AMD Rome has significantly faster L3 cache than Intel (https://www.anandtech.com/show/14694/amd-rome-epyc-2nd-gen/7 https://www.anandtech.com/show/14694/amd-rome-epyc-2nd-gen/7) and generally more of it overall, but it is split among many CCX. This fragmentation can be a problem. --- On the 13900K... At home, I have a 13900K (128G 4090 8T+8TSSD) and use Mathematica often for personal use. I installed it intially in Windows 11 Pro and got abysmal performance in benchmarks (worse than 12900 equivalent processor). With help from Wolfram customer support, I switched to Linux (Ubuntu): the performance is on par with what I'd expect. My hypothesis is that either the Windows scheduler for Windows 11 Pro optimizes for a different performance point than Linux, or that it was oblivious of performance vs. efficiency core (13900K has double the efficiency cores of the previous generation, so if you pick randomly you have a lot more chances to end up in a slow core). This was in the previous minor release of Mathematica, I hope they implemented a workaround in the latest version. I don't think it was a Mathematica bug, but an OS-level problem (I haven't tried, but I can it would be easy to check): many report that stable diffusion works better on Linux than Windows. My personal toy project was a reinforcement learning thing, for which the CPU was the bottleneck on Windows (performance on par with MacStudio M1 Max) and I saw nearly 2x improvement switching to Linux.