sir i want to know about the marking scheme and the role played by boards in iit

I think you should stop worrying about the board weightage and focus on doing well in the JEE Mains.I made the same mistake this time last year.I thought way too much about the board weightage but I realised that thinking about it is useless.I got 200 marks in JEE Mains 2013,got 26k rank(due to my board % which was 87).There`s only one thing I can tell you:prepare well for JEE Mains but don`t neglect your boards.Study for the boards everyday for about one hour.