Definitions
- Basic Input Output System. All computer hardware
has to work with software through an interface. The BIOS gives
the computer a little built-in starter kit to run the
rest of softwares from floppy disks (FDD) and hard disks (HDD).
The BIOS is responsible for booting the computer by
providing a basic set of instructions. It performs all
the tasks that need to be done at start-up time: POST
(Power-On Self Test, booting an operating system from FDD
or HDD). Furthermore, it provides an interface to the
underlying hardware for the operating system in the form
of a library of interrupt handlers. For instance, each
time a key is pressed, the CPU (Central Processing Unit)
perform an interrupt to read that key. This is similar
for other input/output devices (Serial and parallel
ports, video cards, sound cards, hard disk controllers,
etc...). Some older PC's cannot co-operate with all the
modern hardware because their BIOS doesn't support that
hardware. The operating system cannot call a BIOS routine
to use it; this problem can be solved by replacing your
BIOS with an newer one, that does support your new
hardware, or by installing a device driver for the
hardware.
- Complementary Metal Oxide Semiconductor. To
perform its tasks, the BIOS need to know various parameters (hardware
configuration). These are permanently saved in a little
piece (64 bytes) of CMOS RAM (short: CMOS). The CMOS
power is supplied by a little battery, so its contents
will not be lost after the PC is turned off. Therefore, there
is a battery and a small RAM memory on board, which never
(should...) loses its information. The memory was in
earlier times a part of the clock chip, now it's part of
such a highly Integrated Circuit (IC). CMOS is the name
of a technology which needs very low power so the
computer's battery is not too much in use.
- Actually, there is not a battery on new boards, but an
accumulator (Ni_Cad in most cases). It is recharged every
time the computer is turned on. If your CMOS is powered
by external batteries, be sure that they are in good
operating condition. Also, be sure that they do not leak.
That may damage the motherboard. Otherwise, your CMOS may suddenly
"forget" its configuration and you may be
looking for a problem elsewhere. In the monolithic PC and
PC/XT, this information is supplied by setting the DIP
(Dual-In-line Package) switches at the motherboard or
peripheral cards. Some new motherboards have a technology
named the Dallas Nov-Ram. It eliminates having an
on-board battery: There is a 10 year lithium cell epoxyed
into the chip.
- A PC consists of different functional parts installed on
its motherboard: ISA (Industry Standard Architecture), EISA (Enhanced
Industry Standard Architecture) VESA (Video Enhanced
Standards Association) and PCI (Peripheral Component
Interface) slots, memory, cache memory, keyboard plug
etc... Not all of these are present on every motherboard.
The chipset enables a set of instructions so the CPU can
work (communicate) with other parts of the motherboard.
Nowadays most of the discrete chips; PIC (Programmable
Interrupt Controller), DMA (Direct Memory Access), MMU
(Memory Management Unit), cache, etc... are packed together
on one, two or three chips; the chipset. Since chipsets
of a different brand are not the same, for every chipset
there is a BIOS version. Now we have fewer and fewer
chipsets which do the job. Some chipsets have more
features, some less. OPTi is such a commonly used
chipset. In some well integrated motherboards, the only
components present are the CPU, the two BIOS chips (BIOS
and Keyboard BIOS), one chipset IC, cache memory (DRAMs,
Dynamic Random Access Memory), memory (SIMMs, Single
Inline Memory Module, most of the time) and a clock chip.
- Setup is the set of procedures enabling the configure a
computer according to its hardware caracteristics. It allows
you to change the parameters with which the BIOS
configures your chipset. The original IBM PC was configured
by means of DIP switches buried on the motherboard.
Setting PC and XT DIP switches properly was something of
an arcane art. DIP switches/jumpers are still used for
memory configuration and clock speed selection. When the
PC-AT was introduced, it included a battery powered CMOS
memory which contained configuration information. CMOS was
originally set by a program on the Diagnostic Disk,
however later clones incorporated routines in the BIOS
which allowed the CMOS to be (re)configured if certain
magic keystrokes were used.
- Unfortunately as the chipsets controlling modern CPUs
have become more complex, the variety of parameters specifiable
in SETUP has grown. Moreover, there has been little
standardization of terminology between the half dozen
BIOS vendors, three dozen chipset makers and large number
of motherboard vendors. Complaints about poor motherboard
documentation of SETUP parameters are very common.
- To exacerbate matters, some parameters are defined by
BIOS vendors, others bychipset designers, others by motherboard
designers, and others by various combinations of the
above. Parameters intended for use in Design and Development,
are intermixed with parameters intended to be adjusted by
technicians -- who are frequently just as baffled by this
stuff as everyone else is. No one person or organization
seems to understand all the parameters available for any
given SETUP.