But for Toshiba HDD, it has special firmware design: many important firmware modules like head parameters, adaptive parameters, translators, ID information, P-list, etc are stored on PCB. G-list, smart modules, overlay, security subsystem, SFlog and some other not-that-important modules are stored in the platter SA area. Advantage of this design helps to speed up the firmware loading, the disadvantage of this design is to add to the difficulty of hdd repair and data recovery when the PCB is damaged.
For old Toshiba HDDs, ROM is built in the main controller chip and if the main chip is damaged, it will be difficult to repair and recover the hdd. For new Toshiba HDD, the ROM is separated from the main chip and has then the external ROM chip. However, these ROM chips are mainly using BGA package and it makes our soldering work more difficult and time-consuming.