Why is it that, RAM, Hard Disk etc, the size increases dramatically over the years but processors don't get much faster? (is it to do with heat?)
No, even though both show up as 2 CPU in task manager.
HT is a method to utilise underutilised parts of a CPU to excute a second thread (think of a thread as a process).
So basically a 'Core' can do lots of different instructions. Theory is that most programs are not making full use of all of these functions so there are parts of the CPU not doing anything. What hyper threading does is attempt to use these 'unused' parts to run a second thread. Results are very dependant on the applications you use. Best case tests have shown around 30% boost, others have shown that HT can actually slow your system down.
Dual Core, is effectivily having two seperate CPU on one chip. It can excute two seperate threads regardless of what the other core is doing. Programs do need to be optimised for multithreading but expect anything from 60% to 100% speed increase.
BTW, the more cores you have, generally the lower the return rate per core unless your applications are highly optimised for multi-core operations.
To make matters more complicated, you can have 4 core CPU running an application slower then a 2 core CPU with high clock frequency if the application is badly written.
To matter worse, intel mix and match features even within the same CPU family. So you have some i5 CPU support HT, other support Turboboost, some support both, some support neither I think.
Also some AMD CPU sold as 3 core are actually 4 core and can have the 4th core 'unlocked' and there is a whole another topic regarding overclocking where you run a CPU faster then the stated clock frequency.
Hope that clears things up, lol