physical repairs or firmware reconstruction

[Rocky Lane]

Your FAQ mentions physical repairs or firmware reconstruction when a drive is not recognized by the BIOS.

What does the BIOS look for and how? Is there a track on the disk it tries to read? If the trackt is unreadable, can the disk ever be read again?

What are "physical repairs"? What has to be done to the drive?

What is "firmware reconstruction"? Who can do this?

Thanks.

[Alexey V. Gubin]

The BIOS itself does not look at the disk. Basically the BIOS asks "you there", and if the reply is "yes", it then asks "identify yourself, then". The drive itself is responsible for proper identification.
The drive has a chip with a program in it, and there are two options:
1. The chip and program are the same across all drives (and even across different models). In this case the disk-specific data is stored on a disk (platters) itself. The program reads the basic information about the disk (set of platters) from the disk itself.
2. The data about the particular set of platters is recorded in the NVRAM of the chip.
In a design (1), if the track is unreadable, you can still load the data from the same model of the drive; possibly involving a hotswap procedure.

Physical repairs involve replacement of whatever is broken or shorted in the drive. What exactly needs to be done varies with a drive and a problem.

Firmware reconstruction is basically when you lost a part of the firmware (the internal drive control program), e.g. because its part which is stored on a disk itself (platters) became unreadable. Typically a data recovery lab can do this, but the methods and specifics are different for different drive vendors and models. We do not do it (not our specifics).

Hopefully that helps?