Originally posted by MagnonIndeed. The EMP was potent enough that it also took out Luke's X-Wing(he was flying in the vicinity.)
If I understood correctly from Galan's scans in the ownage thread, Vader's suit, its life support systems, and presumably his cybernetics too had just been disrupted by an EMP. It's impressive he could fight at all.
I would note that Vader was force-shielding himself from the attacking Kakrans at the time, but the EMP still looked to have had *some* sort of effect on him.