Hardware Reference
In-Depth Information
Keyboard Controller Chips
In addition to the main system ROM, some systems have a keyboard-controller microprocessor
with its own built-in ROM. The original keyboard controller was an Intel 8042
microcontroller, which incorporates a microprocessor, RAM, ROM, and I/O ports. This was a
40-pin chip that often had a copyright notice identifying the BIOS code programmed into the
chip. Modern motherboards have this function integrated into the chipset, specifically the Super
I/O or South Bridge chips.
The keyboard controller controls the reset and A20 lines and deciphers the keyboard scan
codes. The A20 line is used in extended memory and other protected-mode operations.
Upgrading a Flash BIOS
Virtually all PCs built since 1996 use a flash ROM to store the BIOS. A flash ROM is a type of
EEPROM chip you can erase and reprogram directly in the system without special equipment. Older
EPROMs required a special ultraviolet light source and an EPROM programmer device to erase and
reprogram them, whereas flash ROMs can be erased and rewritten without you even removing them
from the system. On some systems, the flash ROM is not a separate chip but may instead be
incorporated into the South Bridge chip.
Using flash ROM enables you to load the upgrade into the flash ROM chip on the motherboard
without removing and replacing the chip. Normally, these upgrades are downloaded from the
manufacturer's website. Depending on the design, some update programs require that you place the
software on a bootable floppy or optical disc, whereas others configure the program to run on the next
startup (before Windows loads), and still others actually run in Windows as a Windows application.
Some systems allow the flash ROM in a system to be locked (write-protected). In that case, you must
disable the protection before performing an update—usually by means of a jumper or switch. Without
the lock, any program that knows the correct instructions can rewrite the ROM in your system—not a
comforting thought. Without the write-protection, virus programs could be written that overwrite or
damage the ROM BIOS code in your system. The CIH virus (also called the Chernobyl virus) was
one example that could overwrite the BIOS code on certain motherboards. Instead of a physical
write-protect lock, some flash ROM BIOSs have a security algorithm that prevents unauthorized
updates. This is the technique Intel uses on its motherboards, eliminating the need for a lock jumper or
switch.
Note that motherboard manufacturers do not normally notify you when they upgrade the BIOS for a
particular board. You must periodically log on to their websites to check for updates, which you can
then download and install at no charge.
Before proceeding with a BIOS upgrade, you must locate and download the updated BIOS from your
motherboard manufacturer. Log on to its website, and follow the menus to the BIOS updates page;
then select and download the new BIOS for your motherboard.
Note
If a flash BIOS upgrade is identified as being for only certain board revisions of a particular
model, be sure you determine that it will work with your motherboard before you install it.
You might need to open your system and look for a revision number on the motherboard or for
