NT-4 and BIOS interaction after BOOT

Good morning

I would like to know what interactions, if any, and how they take place between the OS and the BIOS after the OS has been loaded and is running. This is to troubleshoot hardware problems so as to anticipate and prevent system crash. The platform is : NT-4 workstation SP6, PhoenixBIOS 4.0 revision 6 and standard hardware.