På wikipedia är väl det här en bra sammanfattning av vad BIOS gör idag.
Citat:
In modern personal computers running modern operating systems the BIOS is used only during booting and initial loading of system software. Before the operating system's first graphical screen is displayed, input and output are typically handled through BIOS. A boot menu such as the textual menu of Windows, which allows users to choose an operating system to boot, to boot into the safe mode, or to use the last known good configuration, is displayed through BIOS and receives keyboard input through BIOS.[citation needed]
However, it is also important to note that modern PCs can still boot and run legacy operating systems such as MS-DOS or DR-DOS that rely heavily on BIOS for their console and disk I/O. Thus, while not as central as they once were, the BIOS services are still important.