PCEngine-FX.com

It is a well known fact that the pc-engine / turbografx can handle multiple layers of parallax
( Soldier blade, street fighter II, dead moon, etc. ). My question is : was this "effect" handled by the hardware ? Or were the game companies forced to "homebrew" this effect because of the pce's lack of a special chip to handle this task ?

No, the PC Engine has no hardware parallax scrolling facility. She can handle one multidirectional scrolling layer at a time, the rest of the magic is up to the coder.