Using Atitool with Nvidia card

How trusty is Atitool for finding the max core and max mem speed for nvidia cards?? will it really find the speeds or might be any danger of frying the card.
I tried my xfx 7600gt xxx edition 650/1600 stock,it took my core up to 713 and it continued going up so i stopped it and said to ask first. By the way the core temp at that speed was 63c at the heating period using stock cooling and no artifacts.