A PC goes through a process when it is
first turned on: the Power-On Self-Test,
or P.O.S.T. Some system boards provide security measures
demand a password before beginning the P.O.S.T. process or allowing
you into the BIOS setup program.
The original IBM-PC (1981) did not provide any security measures or a
BIOS setup program; all it had was a P.O.S.T. If you needed to
configure a PC, you did it with switches and jumpers. A program to
set up the system BIOS and configuration did not come along until the
IBM-PC/AT (1984), and it had to be run from a special boot-up
diskette. The idea of providing a user interface and access to the
system configuration settings within the BIOS did not come along
until about 1986. Today no PC system is made without this valuable
built-in setup feature. Eventually, the security feature of
password-protecting access to the system came along.
If, after turning on your PC, you are prompted for a password instead
of greeted with a fancy logo screen or the technical gibberish that
suggests the system is getting ready to let you use it, then a
security feature has been turned on that we call a
password." Without the right password to get past
this point, the system is basically dead in the water—game
over, do not pass go and collect $200—unless or until you reset
the BIOS setting. But how do you do that without getting past the
password to the setup program?
This hack is also very effective for putting the system board back
into "factory stupid" mode where it
knows nothing about your system components and forgets all of your
parameter tweaks. This is very useful if you've
performed a hack that renders the system unbootable or unstable.
The goal is to get the system to forget that it needs a password and
forget what the password was. The password data is stored with the
rest of the system configuration data in a small amount of memory
that is kept alive using a small battery or internal power cell. To
clear out the data, you need to remove the power from this memory
element. This means the system will also lose any system
configuration that was saved. You'll need to later
reconfigure the system parameters so you can boot your operating
For this and many subsequent hacks, you will be working with
electrical components inside your PC. We want you to get through the
entire book and enjoy your computer for a long time without risk of
electrical shock or component
damage. When the cover is off your PC and you are removing or adding
components—be they add-in cards, RAM chips, CPUs, or
fans—especially when you are handling the screws to hold things
in place, ALWAYS turn the PC's
power OFF and unplug the power
cord from the back of the PC.
Disconnecting the power cord removes the risk of exposure to high
voltages and accidentally turning the power to the system board on.
Disconnecting the power cord also allows the PC chassis to become
ungrounded, which reduces the potential difference between any
static charge in your body and the
chassis so static shocks are less likely.
It is also recommended that you use an anti-static wrist strap
connected to the PC's chassis for further protection
of delicate electronic components.
To perform this hack you will need:
A #1 or #2 Phillips-head screwdriver, or (less likely) a T-15 TORX
driver or a 1/4" hex nutdriver, to open the case
Needle-nosed pliers if you are working with jumpers
A small flashlight or headlamp
With tools at hand, perform the following
Turn the PC off (this means a total shutdown, not merely standby or
hibernate mode) and disconnect the AC power cord.
Remove the cover from your system (this step may require tools,
undoing a thumbscrew, or flipping a latch or two).
Refer to the user manual for the motherboard to find out how to
"reset CMOS" memory. You may also
find a label for specific
jumper or switch settings marked on the
Change the switch setting or jumper position to a specific position
or remove the jumper entirely as prescribed in the manual to clear or
reset the CMOS memory.
Wait 20-30 seconds for the memory to clear out from lack of power.
After 20-30 seconds put the switch or jumper the way it was before
for normal use.
Reconnect the power cord and start up the system to see if the
settings have changed to defaults.
Shut the PC down, disconnect the power cord, replace the cover,
reconnect the power, and power up the PC.
Enter the BIOS setup program to
configure the system as needed. This may include setting the date and
time, selecting disk drive parameters, and selecting which devices
the system uses to boot up with first.
If your system does not have a "reset
CMOS" jumper or switch , the only option is to
locate and remove the coin-style battery
cell (or on some very old PCs, the battery pack), as shown in , that provides the power to the CMOS memory.
Figure 1. System board with coin-style battery used to retain CMOS memory
Follow Steps 1 and 2 above, locate the battery, and remove it. Leave
the battery out of the system for 20-30 seconds, replace it, and
start up the system. The CMOS memory in some systems may retain
settings longer than others. If the CMOS memory does not clear and
you're still stuck, you may need to leave the
battery out for several hours before reinstalling it.Once the system
is able to perform P.O.S.T. and to start booting up the system, you
will need to get into the Setup program for the
BIOS and make a few basic
adjustments, such as:
Setting the date and
Selecting auto-detect or manually setting specific parameters for
IDE hard drives
Setting the boot-device order—diskette drive,
hard drive, CD-ROM, etc.
If you expect to perform more hacks with jumpers, switches, cables,
chips, or disk drives, you'll probably find it
convenient to leave the cover off your PC, but beware: we do not want
to cause more trouble than we're trying to solve.
You could be exposing yourself to dangerous voltages (inside the
power supply) or exposing the internal wires and connections to disk
drives and plug-in cards to your tools, screws, and other wires that
could come in contact with them. At this stage, spilling your
favorite beverage or dropping your tools anywhere inside the PC
chassis is not advised.
You may find one of many possible
"backdoor" passwords for
your BIOS that allow you access to the system setup program and
bypass boot passwords at either of two web