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Role of the BIOS in Hard Disk Access

The system BIOS is the lowest-level interface between the hardware of your system and the software that runs on it. It has several significant roles that it plays in the control of access to hard disks:

• BIOS Interrupt Routines: In order to ensure the interoperability of various hardware and software products, the BIOS of the system is tailored to the needs of its hardware, and provides a standard way of letting software addressing the hardware. These are called BIOS services and are used by many operating system and application programs. They provide a uniform interface to the hard disk, so applications don't need to know how to talk to each type of hard disk individually. (Many newer operating systems today regularly bypass these BIOS services but still may use them for compatibility purposes.)
• Hard Disk Detection and Configuration: Standard IDE/ATA hard disks are configured in the BIOS using various BIOS settings. Modern BIOSes can in fact interrogate modern IDE/ATA disks to determine these parameters, and automatically configure them.
• Hard Disk Interface Mode Support: The BIOS, working with the system chipset on the motherboard and the system I/O bus, controls which types of interface modes can be used with the hard disk. This refers specifically to features such as high-performance PIO modes, DMA modes, and block mode.

Next: The Int13h Interface

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