Game crash

Hello guys,i had and old board asrock g41 vs3 r2.0 intel dual core e5200 4 gb ram (2 kingmax 2 zepelin both at 1333 mhz),hdd 320 wd from 2008,zalman glx 700 w.I upgraded to a new mobo asrock 980de3/u3s3 with phenom x2 b59 unlockable to quad..ive reinstaled windows do a few benchmark of cpu prime test 95 and it doesnt crash while 4 cores unlocked...but i have another problem..at my old sytem i upgraded first to a gtx 560 ti oc frozr ii ...and i had bottle neck...now its seems the bottleneck gone as i upgraded to amd...but...on stock gtx values..i tested wot gta 5 and DMC 4 and ive seen after a few minutes artefacts and flickering and than freeze with a black screen...only in witcher 3 i didnt have artefacts..if a lower memory and core clock by 50 the artefacts are gone...whats the problem?................I tested at my cousin with the same mobo and fx 6300...and after a lot of matches in world of tanks on full hd maximum settings no artefacts with same stock values at gpu....................at my pc i get them after a few minutes...but its crashing only the game..i can ctrl alt delete and end the non responding game and the computer runs fine than...its not freezing all pc just the game..can you help me please?i want to run the stock values without game crashing..(EDIT IVE DONE HEAVEN BENCHMARK ON ULTRA A FEW TIMES BUT NO ARTEFACTS...)

Try using a vga cable and see if the artifacts and flickering are still there. If no problem with vga cable, then the problem is either with the hdmi/dvi ports, or hdmi/dvi cable, or the graphics card is bad.