so my friend have q6600 based system with 4gigs of ddr3 ram a digilite motherboard running a gt 710 with a 10$ psu 450w . i gave him my old r7 250 (working fine) as he just plays league Dota or games like paladins.after adding the r7 the system had random shut down due to cpu overheating.he applied thermal paste to it and now everything works fine. can you guys pls tell me why the cpu overheated when he added a r7 270 which require only 450w of power while his gt 710 was working fine and why thermal paste fixed this problem. Also now he wants to overclock the cpu is this a bad idea?