I was curious whether hyper-threading means twice the number of cores at their full potential or each virtual core has actually half as much power as the physical core. It is easily understood that an i5-3570 will be 4 cores at 3.3GHz for sure, but will an i7-3770 be 8 cores at 3.3GHz or something like 8 cores at 1.65GHz? And if it "is" 8 X 3.3GHz, does it mean it is comparable to a real 8 core xeon at 3.3GHz? Ok, not really a xeon , but is it the same thing as 8 real cores? I guess not, because that would be the stupidest thing to do on intel's part..
No it doesn't. The best way to think about hyper-threading is to think about leftovers. When a core is running a normal thread it doesn't take 100% of the resources. What hyper-threading does for applications that can use it is allow a second pathway for data to enter the core and take advantage of those leftover resourse. If an application can take advantage of hyper-threading you might get 10% or more additional performance. So the first 4 cores will have a clock speed of 3.3GHz and than might get another 10% or more from that.
One more doubt.. What happens to the hyper-threading scenario when one overclocks? Does it become more effective because of the increased performance of the real core (i.e. 10% of 4GHz instead of 10% of 3.3GHz) OR less effective, since the left over which HT was going to use is already used up by the real core?