title: Single-CPU programs running on Hyper-Threading-enabled quadcore CPU
body: <p>I'm a researcher in statistical pattern recognition, and I often run simulations that run for many days. I'm running Ubuntu 12.04 with Linux 3.2.0-24-generic, which, as I understand, supports multicore and hyper-threading. With my Intel Core i7 Sandy Bridge Quadcore with HTT, I often run 4 simulations (programs that take a long time) at the same time. Before I ask my question, here are the things that I already (think I) know.</p>
  
  <ul>
  <li>My OS (Ubuntu 12.04) detects 8 CPUs due to hyper-threading.</li>
  <li>The scheduler in my OS is clever enough never to schedule two programs to run on two logical (virtual) cores belonging to the same physical core, because the OS supports SMP (Simultaneous Multi-Threading).</li>
  <li>I have read the Wikipedia page on Hyper-Threading.</li>
  <li>I have read the HowStuffWorks page on Sandy Bridge.</li>
  </ul>
  
  <p>OK, my question is as follows. When I run 4 simulations (programs) on my computer at the same time, they each run on a separate physical core. However, due to hyper-threading, each physical core is split into two logical cores. Therefore, is it true that each of the physical cores is only using half of its full capacity to run each of my simulations?</p>
  
  <p>Thank you very much in advance. If any part of my question is not clear, please let me know.</p>