Hyperthreading technology

This is a term for Symmetric Multithreading(SMT) on Intel processors. SMT is a strategy which allows several threads to run concurrently by providing multiple physical processors. Actual idea behind is to create a representation of multiple logical processors on the same physical processor to the operating system. Each logical processor has its own architecture state like general purpose and machine state registers, has its own interrupt handling while share the resources like caches and buses of the physical processor.
This is a feature provided in hardware and not software i.e hardware only must provide the handling for interrupts and representation of the architecture state for each logical processor.

A typical SMT architecture

While there is no such need to design operating systems differently for SMT architecture but still performance gains can occur if OS has some knowledge of it. For instance if there is a system with two physical processors each with two logical processor, then if two processes are to be scheduled, then rather than scheduling them on the two logical processors of the same physical processor , it would be a better idea to schedule each on one of the logical processors of the two physical processor . If OS has the knowledge that it is operating on such a system , then it can be of benefit.