Ok so if the gpu doesnot have external power molex it takes power only from the sata connector?
So if I put 6 750 ti that draw 38w each from the sata connector the psu will fail even if it is 700w cause the gpus will only use the sata line and you can't provide 250 w from this line ? Am I right or not?
You need to connect the PCI-E power plugs to the video card in addition to the power plug on the riser PCB (floppy/molex/sata/whatever it is). It is required.
Most of the power will be pulled from the PCI-E power plugs. There are certain parts on the video card that need power from the PCI-E slot though (some 12v, some 3.3v which is taken from the 5v line and down-converted to 3.3v on the riser board). The power draw should not typically pull more than 75 watts; it will likely pull much less is most occasions, or maybe more, depending on what you are doing with your video card. Your best bet is use a multimeter to determine exactly how much power is being pulled through it. But there is no way 250 watts is being pulled throug hit, because thats what the PCI-E power plugs are for.
