Что-то поздно спохватились вы :)
В HT наблюдалось несколько % прироста на многотредовых задачах - за счет преимущества аппаратной реализации переключения между потоками над программной (средствами ОС).
Если бы этого не было - HT бы убрали сразу после ввода Multi-Core, а он остался - в топовых моделях.

Давайте-ка тынц, мимопроходящий.

Лично я нашел за 5 минут в гугле вот что:

Hyperthreading

Most processors of current generations support Hyperthreading. The advantage of Hyperthreading over classical multiprocessing lies in a gain in performance at reduced costs. With the processor types available today, a processor family is entirely offered with or without Hyperthreading.

With Hyperthreading processors, some resources on the chip are doubled so that the CPUs are now capable of executing two threads in parallel. Thus, two virtual or logical CPUs are simulated. To the operating system, a CPU with Hyperthreading appears to be two CPUs and will be controlled as such. This increases speed if the operating systems and applications are suited for higher speeds. Windows is designed as an operating system capable of Hyperthreading, and particularly within terminal server environments, numerous individual users simultaneously work with quite a large number of mostly small applications so that Hyperthreading can be expected to lead to a performance increase.

Measuring has shown that the increase in performance due to Hyperthreading is the largest for systems with low to medium load. The performance gain is lower for systems working at their load limit. Moreover, the performance gain on a mono-system is higher than that on a multiprocessor system.

A measurement sequence was run on a PRIMERGY RX200 with two processors; one set of simulations each was carried out with enabled and disabled Hyperthreading. The same number of users (101) was simulated in both cases. For terminal server applications, Hyperthreading resulted in a reduced load on the system. The CPU load could be lowered by 31% as shown in the diagram. When the test was run on the PRIMERGY RX200 and 101 users without Hyperthreading, a CPU bottleneck was indeed detectable. The response times of Terminal Server were no longer within the specified time slice.

However, the system complied with the specified response times again when the relief of the CPU load was achieved by Hyperthreading. This means that with a medium-load profile the number of terminal server users operating on the same PRIMERGY system can be increased by approximately 20% as a result of Hyperthreading. A reduction of the CPU load cannot be reflected 1:1 in an increased number of users because the CPU time in the high-load range does not rise on a linear scale, but rather in an accelerated manner (see the diagram in the section “Behavior at High CPU Load”).

The measurement method with a variable number of users was applied to determine the absolute number of users for systems with and without Hyperthreading. The diagram shows the measuring results. The PRIMERGY system used for the test was a PRIMERGY RX300 S2 with one or two processors with different clock frequencies. For this comparison, all processors were equipped with a 1-MB SLC. Hyperthreading was alternatively enabled (“HT on“) or disabled (“HT off“). It can be seen that a larger number of users can work with Terminal Server when Hyperthreading was enabled. The performance gain due to Hyperthreading for a slower mono-system is much higher than for a fast dual system.

Модератор: Отредактировано

P.s. это с сайта MS, конечно

Windows - нативная многопоточная ОС (ядро NT), и польза от HT есть всегда (всегда работают десятки сервисов и несколько программ пользователя).
В цитате наблюдается увеличение числа терминальных сессий на включенном HT по сравнению с отключенным.