can i start my computer?

That depends largely on your power supply. My 2nd Core2Duo based computer had 8 pins for CPU power, but my old high end PSU was more than powerful enough to run the system with it's single 4pin connector.

However, newer CPUs are much more picky, and may not play as nice. Haswell based systems in particular need very well regulated power that an older PSU will simply not be able to provide. If your PSU is 6+ years old and only has a single 4pin CPU power connector then I would suggest upgrading to a newer PSU rather than risking feeding bad power to the system.