Hey Ayush,

Yes, Anyone can give exam in whichever stream he is interested in GATE. There have been many people who have done this and excelled. In fact, there was a person from Mechanical engineering who had interest in software field, next what he did was appeared in GATE from CS branch and secured AIR 1 in GATE 2015.

Although if your target is some PSUs and other recruitments through GATE then it could be a barrier to give GATE from other stream as opposed to your graduation stream .These companies have some branch specific criteria along with GATE stream paper which you have appeared in. Same goes for some courses in IIT’s & NITs.