Can the PSU not be coonected to the CPU and the computer still work?

[uncle.rat97]

Just as the title, when i disconnected my old PSU to change it with a new one i saw that the CPU cable was not connected (a friend of mine checked the pc when it was not working), can there be cables from other parts that send energy there or it has to be connected otherwise it would not work?

 

[Dark Lord of Tech]

CPU needs to have the 8 pin connected for power.