PCB : BIOS Transfer +... PCB ordered-in this website
Western Digital has 2 types of PCBs.
Type 2 HDD board has an 8-legged BIOS chip that must be swapped. See How To Swap HDD PCBs
Type 3 hard disk drive PCB has a missing chip, and PCB firmware is stored in the big Controller Chip. That chip can be reprogrammed or transferred by a professional with a BGA Rework Station.
For each PCB, we specify if there is a BIOS chip or not. In addition this BIOS chip is shown in the picture.