Lets take a look at the PCB there are often several chips on a PCB but what do they do? Do they contain the firmware or is that resident on the hard drive? The IC chips on the logic card are nothing more than empty chips, they have to be programmed to deliver their functions and complete the circuit. Originally all hard drives stored firmware in the ROM, unfortunately this limited the code and functions of the hard drive. Currently the firmware is stored in the SA Service Area of the hard drive known to the manufacturer as a reserved area. The firmware is organized into modules and controlled by the manufacturers own operating system. The ROM chip nowadays contains minimal amount of code, some companies now have nothing more than the loader on the ROM chip.

The ROM chip is either within the main controller or as a separate chip, 90% of hard drives have a flash ROM. If the disk contains a flash ROM then the microcontroller reads the firmware from the ROM if not it has to use the internal ROM.

Some of the information is the same for all models by a manufacturer and this is usually the controller firmware. These modules will work on other hard drives without any changes and there will be no problems and no need for a hard drive data recovery. However this is not true of all modules and takes great knowledge to understand the firmware modules and what can and cannot be transferred between drives.

Some parts of the modules are designed to specifically work with only one model of hard drive. Such information as the disks serial number held in its certificate, this certificate or CERT module holds information such as information about heads, sectors and cylinders. When the hard drive is turned on it initializes the heads are then counted, if the information no longer matches the info in the CERT module then the disk will be unlikely to switch to ready.

On some hard drives that have been refurbished faulty heads may have been turned off, therefore in order to use this type of hard drive for its logic card as a donor you would require PC3000 to make some changes to the firmware.

One of the biggest problems is the list of defect tables; these modules are specific to only that drive as they basically contain information regarding the bad sectors on the disk in hand.