Are Test and set primitives as powerful as semaphores?

I get confused because i don't know if it is possible to use Test and Set primitives in case where more then one process can be enter in critical section at the same time.

Your hunch is correct, they aren't equivalent. Test-and-set has a consensus number of 2, which means, roughly speaking, that it is only able to efficiently synchronize between 2 processes. See Why is the consensus number for test-and-set, 2?. Semaphores allow synchronization between an arbitrary number of processes (assuming no bound on the number of processes waiting on a semaphore).

It isn't really a “fair” comparison, since test-and-set is a hardware primitive while semaphores are a software interface. But if does show that test-and-set isn't sufficient to implement (wait-free) semaphores.

StackExchange Computer Science Q#83146, answer score: 5