To summarize what happened in 2015: I have converted the cutoff scores to rank using the data from GATE CSE 2015 Result Responses and GATE CSE 2016 Result Responses
(using ~ for very close approximation)
IISc CSA (Direct admit) : ~90 in last round and ~102 in spot round. ~300-400 for OBC
IISc CSA Research Interview cutoff: 1021 in 2015 and 645 in 2016
IISc CDS M.Tech Interview cutoff: ~385 in 2015 and ~85 in 2016
IISc CDS Research Interview cutoff: ~1100 in 2015
IITB TA: 89 in last round. ~150-300 for OBC
IITM: ~160 rank (1 person with rank 391 got admitted in spot). ~350-500 for OBC
IITKgp CS: 144 in last round and ~200 in spot
IITKgp IT: 180 in last round and ~220 in spot
(IITKgp had internal sliding and those who opted for inter disciplinary branches got promoted to CS before spot round happened)
IITD MCS: Had interview cutoff which was ~230 rank
IITD EET: Had interview cutoff which was 470 rank in 2015 and 441 in 2016
IITK: Had interview cutoff 476 rank in 2015 but ~370 in 2016 (could fill only about 38/70 seats in 2015)
IITK MS: Interview cutoff 413 rank in 2016
IITG: 291 in last round and ~320 in spot. ~800-1200 for OBC
IITG TCS: Had interview
IITH: was mostly similar to IITG/R but I don’t have exact values.
IITR: ~320 in spot, now has self financing seat for which last rank should be slightly lower
The cutoffs in 2016 seem much higher for interviews – IITK and IISc CDS for example and I have no explanation for that. Also, one of the most disturbing factor in 2015 was IITK, IITH wasting tens of seats for the reluctance to do a spot round or maintaining a waiting list. Shows how good the administrators in those places are – they simply didn’t do anything to fill the seats when students left and joined IITB/IISc on further rounds. IITKgp Director being a great person was ready to do a spot round in 2015 though it was the first time they conducted direct admit and he saved the lives of many students. Hope IITK and H learn something.
But things changed in 2016, due to the great effort of Prof. Ganguly IITK conducted a last round admit and more than 20 people got admitted. IITM also had many rounds of call letters to ensure proper seat filling. Hope 2017 also follows the same and no seat is vacant.
For CCMT admits to NITs and some central universities, full data is available for all categories. This can be used for the last rank estimates of SC, ST, PH categories even at IITs.