A few months ago the power supply on my desktop went dead. and so i decided i would replace it along with my cpu. my cpu was a 2.2 gh 4 core phenom. i got a 3.2 gh 3 core anthlon. Now the first time i restart the witcher 2 launcher i go into options to see if i'll get any different performance and it changes from high spec which it had detected earlier to medium spec. Why is this. Is witcher 2 that reliant of a quad core processor that a more powerful three core will give less of a performance? If not what else is going on.

Don't trust those auto-detect settings. Just set it for med and then tweak settings until you find your sweet spot.