Why cpus don't have more than 2 threads by core?
Why cpus don't have more than 2 threads by core?
They don't always run on two threads per core. This is known as "hyperthreading." The first CPUs had just one core and one thread. Earlier models like the 8086, 286, 386, and 486 also followed this pattern—one core, one thread. The Pentium and Celeron lines improved speed but kept that single-core, single-thread design. The Pentium 4 introduced a variant called "Pentium 4 HT" with hyperthreading, giving two threads per core. Performance gains led to wider adoption. Not every processor supports hyperthreading; for example, the 9700K has eight cores but only eight threads, and the Ryzen 5 3500X has six cores with six threads. The reason most CPUs stick to two threads per core is because changing that would require rewriting software to handle more than two threads simultaneously.
Certain CPUs support 4-way multithreading, though it's typically found in data center and machine learning applications. The Xeon Phi series, for instance, implements 4-way SMT, meaning a 64-core processor can handle 256 threads simultaneously.
Thanks everyone, it's great to learn this tech is real even if it's set up on servers. I hope it eventually reaches our desktops.