@wik_a, Get your fact straight "mannay" 
Sumair, For example: Mercedes has both twin turbo and bi-turbo (600 and 65). Bi-turbo means there is a turbo for each bank of of cylinders (Parallel). And they are located on opposite ends of the motor, Both are same size.
Twin Turbo's are a completely different setup. They have 2 turbo's(one bigger than the other) mounted onto one larger turbo manifold. There is a smaller turbo that spools up to create less turbo lag, at which point a larger turbo kicks in for the higher boost. One feeds off the other. Hope you understand 
Btw, talking about 65 AMG, Man, S65 AMG is unmatched beauty and the beast at the same time
p.s, You've been busy. Sumair?