What's the difference between real dual-touch and fake dual-touch?

Question

I have a Xperia X10 Mini Pro and by some ungodly reason it's dual touch feature is not working. I have searched around the net and I have seen here and there people use terms such as real dual-touch and fake dual-touch.
I don't really understand what's the difference here? Can the dual-touch ability be faked and how is that possible?
By the way, if anyone can tell is it possible to activate the dual touch feature in my phone I would be super thankful.

Answer 1

Multitouch touch screen digitizers handle (2,3,4...) or more input fingers at a time at the hardware level.
Single touch devices handle only one finger at a time even if 2 or more are present. If you touch with a 2nd finger, the detected touch will "jump" from the first finger to the second finger location.

Install a touch screen visualizer or test application like Z device test. You can watch a video how it looks with one finger on youtube (which has fake dual touch and has some flaws).

So what a fake dual touch driver does is this:
It basically detects "jumps" of the finger and assumes it comes from a second and just keeps reporting a fixed virtual event (coming from the last known position from the (now vanished) 1st finger touch) while the 2nd touch is from your actual finger and reported regularly.

Answer 2

The difference between real dual-touch and fake dual-touch has to do with how the screen is built. Real touch screens have an additional layer to allow for additional inputs. There are ways to emulate dual-touch with software. This is helpful in the case of your particular phone.

This XDA forum page has a list of updates for particular ROMs including 2 stock ROMs which enable fake dual touch.