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Can you share any more details about the workload? Always interesting to hear of something like that which isn't a useless microbenchmark.

Does it use vector? What can you hit with SMT disabled?

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It’s a backtracking search program looking for integer solutions to a specific problem. I’ve tuned a series of bloom filters to fill my L2 cache so that I rarely have to touch main memory (this alone took my IPC from 0.1-0.3 to 3.0 per thread). Without SMT it’s 4.6 IPC/core.

I think it’s only able to exceed 4.0/thread with SMT off because of a uops cache? From what I’ve read the Zen5 front end only had a 4-wide instruction decode per thread.

coded entirely or partially in assembly, i presume?

Entirely in C. Compilers are pretty good these days. Almost every time I try to outsmart them I make things worse.

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