HCL = From Delhi (I know Tamils will jump, but check)
The reason is simple. Software is all about team culture and english.
Where as Tamils is all about tamil team culture and tamil.
However, as you can see Tamils are there in good positions in the aforementioned companies. Reason being infested. Wherever they go, they will bring five with them.
And from Chennai there is not a single company which is of repute and there never will be.
Regionalism is the core strength. They can not survive on pure talent fight.