IISc Bangalore cutoff 2021 for GATE was 680 for M.Tech CSE program. Different IITs have different GATE cutoffs for their CS Major. Usually, the required cutoff stays with the rank band of 700-750. In 2021, the required GATE cutoff for CS at IIT Madras and IIT Kharagpur were 816 and 776 respectively.
Every IIT has different cut-offs. IISC and the old IITs have much higher cut off than the new IITs every year.
But generally, if you have a rank around 700 to 750 you will get an IIT. IISC always has the highest cut-off as it is one of the best institutes in the country. To get into the IISC CS branch your GATE rank must be under 100. For older IITs, mostly the required GATE rank is 300 to 350. These numbers vary depending upon the difficulty level of the paper on that particular year. For any institute, the required rank that year also varies depending on the gender, and caste of students, etc.