Quote Originally Posted by kl0012 View Post
You have no idea what you talking about. Have you?
Your comparisions are really wrong and misleading.
Interleaved hyperthreading (only one thread at time can be actived on each core) is used only in itanium. All x86 hyperthreaded cores can really handle 2 threads at time (depending on available execution resources). But since in most cases there are available execution resources (a single thread rarely utilize even 70% of available core execution resources), so HT mostly shows positive effect. This is really simple and elegant way to utilize resources which are already in place but not used.
Actually hyper-threading was criticized for being energy-inefficient. For example, ARM has stated SMT can use up to 46% more power than dual core designs. Furthermore, they claim SMT increases cache thrashing by 42%, whereas dual core results in a 37% decrease.

Not to mention that in May 2005 Colin Percival demonstrated that a malicious thread operating with limited privileges can monitor the execution of another thread through their influence on a shared data cache, allowing for the theft of cryptographic keys.

Hyperthreading is largely a strong negative effect to any system.