Some dead hard drives are caused by dead PCB or dead ROM and it's necessary for users to find one compatible PCB and install it to the patient hard drive.
For patient hard drives with external ROM chip, users need to remove the ROM chip and flash new ROM content to it or flash new compatible ROM contents to a good ROM chip and solder to the donor PCB.
One thing is important to remember: the ROM and the SA must be in the same hdd group which makes them compatible with each other to make the hdd work properly.
For patient hard drives without external ROM chip, users need to manage to regenerate the original ROM or flash new donor ROM with the same microcode to it. In the new version of WDII, to flash new ROM for drives without external ROM chips will be added.