Most likely the PS.
Most likely the PS.
Well seeing that css runs on steam n steam is prone to auto update I would suggest 2 see if there were ne updates done that causes issues with ur vid card n if so there will be patches to fix that.....also 2 c if its ur vidcard go into css options and put all vid opts on lowest and c how it runs, but b4 u do that first make sure cpu usage is 0 by turning of all background running programs like antivirus n stuff then just atl ctrl del and check usage (run it with cpu usage at 0 with reg vid opts and then lowest if it still runs the same) if that doesn't work, open the in game console and type MAXfps=100 n c how it runs....and if it still runs same dl prime (I think there's a free dl there sum where on da net) and run it over night if you wake up in morning n ur pc is still on then its a software issue cause if there was ne problems with ur hardeware prime would not run all night....hope that was helpfull let me know if u have ne question at all don't hesitate to ask