What's the function of the BIOS in a modern OS? Is it still used after booting? And is there some kind of BIOS API?
+10
A:
The BIOS is still the first thing that runs on the just-started CPU and responsible for getting the motherboard hardware turned on, setting basic chipset modes and registers, initializing some hardware, and running the code that loads the kernel.
The BIOS is usually not used once the kernel is loaded, and depends on a 16-bit execution environment as opposed to the 32- or 64-bit protected mode environment that a modern kernel operates in.
The boot loader normally does require the BIOS IO calls to get the kernel into memory. The BIOS is being replaced even in this role by newer boot-time software such as Coreboot to provide faster boot times. EFI will one day replace the traditional BIOS, and hopefully the boot loader, passing control directly to the kernel after loading it from storage.
The discovered hardware configuration, memory range settings, and ACPI metadata tables are probably the only BIOS-based data used by the OS after the kernel is loaded. Any runnable ACPI code is encoded as ACPI Machine Language and is interpreted by the OS.
Any good traditional book on MS-DOS assembly programming will include information on the BIOS programming interface. Check out The Art of ASSEMBLY LANGUAGE PROGRAMMING
Joe Koberg
2010-03-29 18:23:10
Lots of BIOS code also executes during power management stuff, on the way in and out of standby. (Not explicitly part of ACPI, but code embedded in SMI handlers that gets invoked during ACPI events.)
msemack
2010-03-29 19:27:30
A:
The biggest benefit to having OS control over BIOS now is to control hardware level variables such as fan speed, temperature gauges, etc.
dmanexe
2010-03-29 18:23:43