Question to i3 sandy bridge owners (single thread cpu usage)

Within the Windows task manager you will see 4 threads and a Window showing total CPU usage. With the Intel® Core™ i3-2120 you will see four windows for the threads and if you are running a single threaded application you would see that thread box running high but you would only see the total cpu usage topping off at under 25% (since the other core and the two threads from hyper-threading is not being used).

Thanks for answer. So if I understand correctly, it will show 25% usage but the whole physical core will be used by that single thread app, yes?

EDIT:
In case someone is interested, I did a research and it's exactly that way. Every of the 2 logical threads on one physical core has the full acces to core - so it means, when you run real time single thread app (game), it will use full physical core, but task manager will only show 25% usage (because it divides 100% by numer of threads and hyper threading is more of hardware thing so the task manager can't display it properly).

This gets into understanding how hyper-threading works. Basically the best way to think about hyper-threading is to think about leftovers. When an application is using a core rarely does it use all of the resources of that core. What hyper-threading does is it allows a second pathway for information enter the core and take advantage of these leftover resources. In most cases where an application takes advantage of hyper-threading you are going to be able to see about 10% or so performance boost from hyper-threading. Lets say you are running an application that is using a both cores and the first thread from hyper-threading.

Intel® Core™ i3-2120
Core 1 |thread 2 |Core 2 |Thread 4
100% 100% 100% 0%

Total usage 75% or something like this.

Brilliant! Thanks.