BIOS – What motherboard BIOS does for a PC

All motherboards include a small block of Read Only Memory (ROM) which is separate from the main system memory used for loading and running software. The BIOS will most likely be stored in a 32-pin chip, which can typically be identified by a silver or gold sticker that shows the name of the BIOS company – such as AMIBIOS, AWARD or Phoenix – and a code that indicates the version of code it contains. If its rectangular in shape, it’s what is known as a DIP (Dual In-line Package) chip. Older motherboards may have 28-pin DIP BIOS chips. If your BIOS chip is square with connections on all four sides, it is in a PLCC (Plastic Leaded Chip Carrier) package. A locating notch indicates the orientation of pin 1. The ROM contains the PC’s Basic Input/Output System (BIOS). This offers two advantages: the code and data in the ROM BIOS need not be reloaded each time the computer is started, and they cannot be corrupted by wayward applications that write into the wrong part of memory. If you have a DIP or PLCC chip that’s actually soldered to your motherboard, you’ll not be able to upgrade it by replacing the ROM. Modern-day BIOSes are flash upgradeable, meaning they may be updated via a floppy disk or, sometimes, through Windows, to ensure future compatibility with new chips, add-on cards and so on. The BIOS comprises several separate routines, serving different functions. The first part runs as soon as the machine is powered on. It inspects the computer to determine what hardware is fitted and then conducts some simple tests to...

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