IIT Madras - Indian Institute of Technology

No, you are not able to get admission on basis of CBSE board marks. You have give JEE Mains for IIIT and JEE Advanced for IIT.

I am sending you an authentic link from where you get all information about the cutoff for IIT CHENNAI. The cutoff are on the basis of different types of parameters. You check there. link-https://www.shiksha.com/college/iit-madras-indian-institute-of-technology-adyar-chennai-3031/cutoff.

The eligibility criteria of DMS IIT Madras for MBA course is Graduates (or professional qualification equivalent to that of a University degree recognised by the UGC) in any discipline with first class or 60% marks (55% for SC/ST/PD) earned in their degree from a recognised/reputed University. IIT Graduates who have obtained a CGPA of 8 and above on 10 are exempted from the CAT score. So your academic profile is good enough for DMS IIT Madras for MBA course. The expected CAT cutoff for DMS IIT Madras for MBA is above 98. Hence, you have to score above this.