Especially in HPC there are lots of workloads that do not benefit from SMT. Such workloads are almost always bottlenecked on either memory bandwidth or vector execution ports. These are exactly the resources that are shared between the sibling threads.

So now you have a choice of either disabling SMT in the bios, or make sure the application correctly interprets the CPU topology and only spawns one thread per physical core. The former is often the easier option, both from software development and system administration perspective.

HT cores can still run OS stuff in that case as that isn't really in contention with those. Tho I can see someone not wanting to bother with pinning

>Especially in HPC there are lots of workloads that do not benefit from SMT...So now you have a choice of either disabling SMT in the bios

Thats madness. Theyre cheaper than their all-core equivalent. Why even buy one in the first place if HT slows down the CPU? Youre still better off with them enabled.