alt Hacker NewsIn nearly every generation of Intel chip where I needed to care about whether hyperthreading was a net positive, it was either proven to be a net reduction in throughput, or a single digit improvement but greatly increased jitter. Even if you manage to get more instructions per cycle with it on, the variability causes grief for systems you have or want telemetry on. I kind of wonder why they keep trying.
I don’t know AMD well enough to say whether it works better for them.
Whether SMT a.k.a. hyperthreading is useful or not depends greatly on the application.
There is one important application for which SMT is almost always beneficial: the compilation of a big software project, where hundreds or thousands of files are compiled concurrently. Depending on the CPU, the project building time without SMT is usually at least 20% greater than with SMT, for some CPUs even up to 30% greater.
For applications that spend much time in executing carefully optimized loops, SMT is usually detrimental. For instance, on a Zen 3 CPU running multithreaded GeekBench 6 with SMT disabled improves the benchmark results by a few percent.