TUTORIAL ON POWER ON SELF TEST CONTINUES..............
(In early BIOSes, POST did not organize or select boot devices, it simply identified floppy or hard disks, which the system would try to boot in that order, always.) The BIOS begins its POST when the CPU is reset. The first memory location the CPU tries to execute is known as the reset vector . In the case of a hard reboot , the northbridge will direct this code fetch (request) to the BIOS located on the system flash memory . For a warm boot , the BIOS will be located in the proper place in RAM and the northbridge will direct the reset vector call to the RAM. (In earlier PC systems, before chipsets were standard, the BIOS ROM would be located at an address range that included the reset vector, and BIOS ran directly out of ROM. This is why the motherboard BIOS ROM is in segment F000 in the conventional memory map.) During the POST