XPS 15 9530 CMOS

It does not have one.

Oh .... So how does one flush the bios if by chance it gets corrupted or unlock password?

You can reset the firmware by holding the power button for about 30 sec with the the power disconnected.  

The system passwords are stored in EEPROM, not battery-backed memory, so they're on removed only with a master code obtained from Dell support (upon verification of ownership of the system). 

@ejn63​ interesting, so I'm guessing one would have to paid for this master code from Dell?

Unless the system is under warranty, yes -- losing the master password means a paid support call.

Is it still under warranty if one were to buy a laptop from someone or company within the warranty period, can the warranty be transfer over to a new owner?

Yes, as long as you're buying from the registered owner or the seller can verify the registered owner's details with Dell.  No, otherwise.

If this is a system where the registered owner does not know the password, make sure they deal with the issue before you buy.