what do you mean by can start? it requires 2x pci-e 1x6 pin you must connect both connectors to the video card. the 6+2pin is just a 6 pin with extra 2 if you are using a videocard that needs a 8 pin connector.
so yes both will work, the 6 pin ano and the 6+2 pin (with only the 6 connected) but don't forget to connect all of them.