A program has to be specifically designed to make use of multiple cores. Unfortunately, there many, many tasks which just cannot be split into separate threads to run on multiple cores at once. It just cannot be done. And of the tasks which can be, actually programming it is a royal pain in the arse. Multithreaded code is difficult to get your head around to begin with, and it adds in all kinds of potential complications (threads interfering with each other, threads trying to access the same file at once, etc). Not to mention the problems it can cause are incredibly random and difficult to debug.
As a result, games don't tend to use more than a couple of cores, and even then they tend to perform most of the work on a single core (though this does vary massively between different games, of course. Some do it significantly better than others). Developers are getting better at doing multithreading though, so hopefully we should see the number of cores games make good use of increase as time goes on.
so the OS that says having HT on a quad is a virtual octa is wrong? screw OS makers.
HT can give a small boost to some types of applications, but it's not a massive boost, and (especially if it's a quad-core cpu already), I highly doubt it will give any boost at all to games. Even in the most optimal situation, it would not in any way shape or form come even close to being equivalent to an octa-core cpu (Not that an octa-core cpu would give any real boost to most games either).
