The BIOS programs

The BIOS programs
During start-up. the BIOS programs are read from a ROM chip. BIOS is abbreviation of Basic Input Output System and those
are programs, which are linked to specific hardware systems. For example, there is a BIOS routine, which identifies how the
PC reads input from the keyboard.
BIOS is a typical link in the IBM compatible PC design. The BIOS programs control hardware, the user (programmer) controls
hardware via a call to BIOS.
BIOS typically occupy 1 MB, and the programs are saved ROM chips on the system board.
During start-up, BIOS is read from ROM chips. That information is supplemented with the system data saved in CMOS.
Furthermore, there is BIOS code on the expansion cards. The expansion cards are external hardware, as interpreted by the
system board, and the BIOS code, which is linked to the expansion card, must be included in the configuration. Therefore,
this expansion card ROM is read during start-up, and the program code is woven together with other BIOS data. It is all
written into RAM, where it is ready for the operating system, as you can see here:

Otherwise, the BIOS routines are not always in use. They can be regarded as basic program layers in the PC. Many

programs routinely bypass BIOS. In that case, they "write direct to hardware", as we say. Windows contains program files,

which can be written directly to all kinds of hardware - bypassing BIOS routines. One example is the COM ports. If you use

the BIOS routines connected with them, you can transmit only at max. 9600 baud on the modem. That is insufficient.

Therefore, Windows will assume control over the COM port.

BIOS-update

BIOS programs can be updated. The modern system board has the BIOS instructions in flash-ROM, which can be updated.

You can get new BIOS-software from your supplier or on the Internet, which can be read onto the system board. The loading

is a special process, where you might need to change a jumper switch on the system board. Usually, you do not need to do

this, but it is a nice available option.

ATX

The latest PC electronic standard is called ATX. It consists of a new type system board with a specific physical design smaller

than the traditional board (30.5 cm X 19 cm). The I/O connectors COM1, COM2 and LPT, keyboard, mouse and USB are

mounted directly on the system board. The ATX board requires specifically designed chassis's with an I/O access opening

measuring 1¾ by 6¼ inch. ATX is designed by Intel, but has gained general acceptance.

The ATX system board is more ”intelligent” than the ordinary type. In a few years, it will be wide spread. It includes advanced

control facilities, where the BIOS program continually checks the CPU temperature and voltages, the cooling fans RPM, etc. If

over heating occurs, the PC will shut down automatically. The PC can also be turned on by for example modem signals, since

the power supply is controlled by the system board. The on/off button will turn the PC "down" without turning it completely off.

If you want a PC designed for the future, the ATX layout is what you should go for.