| Computer Start-Up |
|
| The computer start-up process can be divided
into three basic steps: Power On Self Test, BIOS, and Boot (or Bootstrap). Troubleshooting
system start-up problems can involve looking at one or more of these steps. |
Start-up Process
(Click to Enlarge) |
|
| When Your Computer Won't Start
Although many things can go wrong with a computer, perhaps the most frustrating is when your
computer won't start at all. This is true, in part, because when your computer fails to
start you can not use diagnostic tools to help you determine the problem.
If your computer won't start at all, the power light does not come on and the cooling fan is
not running:
- Check if the wall outlet you are using will it run another appliance such as a small lamp.
- Change the wall outlet you are using -- perhaps there is inadequate voltage.
- Check to make sure that the computer's electrical cord is securely plugged in at both ends.
Switch it with another cord if you have one available to you.
|
|
| If none of these steps help, it is likely your power
supply has gone bad. Power supplies are potentially dangerous units and a
professional should replace your power supply if you need a new one. Never open up a power
supply box. |
Power Supply
(Click to Enlarge) |
| Having a bad power supply can be the cause of many problems that may not
initially point to that component. For example, spontaneous reboots or freezes and even
memory parity errors can be traced to faulty or inadequate power supplies.
It is almost always easier, and often cheaper, to replace a defective power supply rather than
repair it. If you do have to replace your power supply, be mindful of the physical
requirements (shape, location, screw-hole positions and so on). |
|
If there is no power light, but your cooling fan is running:
- Perform the three steps listed above.
- Open up your computer and make sure that your 4-pin power supply
cables (there are usually two) are securely attached to the motherboard.
If none of these steps help, you likely need a new power supply. |
Power Cable
(Click to Enlarge) |
If your power light is on and your cooling fan is running, but there is no
computer activity (you hear no beeps at start-up):
- Open your computer and make sure your power supply cables are securely attached to the
motherboard.
- Examine your motherboard for metal pieces that might be touching other metal pieces (such as
screws or the motherboard's seatings). These could be shorting out your motherboard.
- Check the seating on all the other expansion boards in
your computer. An expansion board that is not seated securely can cause a short.
- Make sure all other cables inside your computer are
securely seated and in good condition. Look for frayed or crimped edges.
- Check that your CPU is inserted properly in its socket,
that it is cool, that the CPU heat-sink/fan works and that it is fitted correctly.
- If your CPU has a tension lever, make sure it is closed and locked.
|
Expansion Board
(Click to Enlarge)
Cables
(Click to Enlarge)
CPU
(Click to Enlarge) |
If you hear two or more beeps at start-up, but there is no video:
- Open your computer and make sure your video board is seated properly it its expansion slot.
|
|
|
| Power On Self Test
The Power On Self Test (POST) is the first set of instructions executed during the start-up of
your computer. You can recognize it during the RAM test, which is one of the system
components that the POST checks, along with the other key components on the motherboard. The
POST order of execution looks like the following:
- Information about the graphics adapter
- Information about the BIOS (name, version)
- Information about the RAM (counted)
|
|
| If the POST detects an error or errors in the system, it will write the error
messages on the screen. However, if the monitor is not ready, or if there are video card
errors, it provides an audible code. If a catastrophic fault has been detected in the Power
On Self Test that your computer does at start-up, the number of these audible beeps can be
indicative of the type of failure. |
|
| These beeps (or beep code) can be useful in troubleshooting problems prior to the
initialization of your computer's video system. The number of beeps is dependent on your
computer's particular BIOS and is unfortunately not
standardized across manufacturers. If you can match your beep code to your particular BIOS
and version, you can accurately diagnose problems with your CPU, RAM, motherboard, video board, or
drive controller. |
BIOS
(Click to Enlarge) |
| Your system's beep codes should be in the written documentation for your
motherboard, or obtainable from the manufacturer's web site. |
|
|
| The following is an example of beep codes from American
Megatrends: |
| 1s (short) |
System RAM refresh failure |
| 2s |
Memory parity error |
| 3s |
Base 64-kbytes memory failure |
| 4s |
System timer failure |
| 5s |
CPU failure |
| 6s |
Keyboard controller Gate A20 failure |
| 7s |
Virtual mode exception error |
| 8s |
Display memory read/write error |
| 9s |
ROM BIOS checksum error |
| 10s |
CMOS shutdown register read/write error |
| 11s |
Cache memory error |
| 1l (long) - 3s |
Memory test failure (non fatal) |
| 1l - 8s |
Display test failure (non fatal) |
Your system documentation or the manufacturer's web site may include recommended
solutions to these error codes. For example, from American Megatrends:
- For 1-, 2-, and 3-beep errors try reseating the system's memory modules. If that
fails, it is possible that 1 or more memory modules are bad.
- For a 6-beep error, try substituting a different keyboard, or reseating the keyboard
controller chip.
- For an 8-beep error, try reseating your video card or a different video card (if your system
has a separate video card).
- For 4-, 5-, 7-, 9-, and 10-beep errors, it is likely that you will need to have your
motherboard repaired or replaced.
|
|
|
| CMOS Setup
The CMOS RAM chip maintains a small amount of information that is essential for your computer
to start-up properly. This information includes data about your floppy drive and hard disks,
your keyboard, your CPU, cache, boot sequence and much more. These data have to be set up
correctly in order for your computer to operate properly. In modern systems much of this
set-up is automatic, but occasionally you may need to manually configure your
CMOS Setup. In general, you should leave these settings
alone unless you are familiar with what you are doing, or you have no other choice. |
CMOS Setup
(Click to Enlarge) |
| Keep track of any changes you make to your CMOS Setup settings.
Because your CMOS settings are dependent upon your computer's battery, it is useful to make a hard
copy (write them down). This way, in the event that your battery fails,
you have a backup copy. |
|
| If your video works but you see a message indicating a setup problem, you will
need to enter into your CMOS Setup in order to look for differences in your CMOS system parameters
and your hardware configuration. How you enter your Setup routine will be dependent on your
BIOS manufacturer -- for example, American Megatrends' CMOS Setup is entered by pressing the
delete key during the POST. Your system documentation will tell you how your particular CMOS
Setup can be entered. |
|
Once you are in CMOS Setup:
- Carefully check each entry and make sure that they are reflective of your actual hardware
configuration -- in particular check that installed memory and drive parameters are correct.
Some parameters, such as ones for the hard disk are usually automatically set on modern system,
however, you may need to enable the drive in CMOS Setup in order to have the system recognize
it.
- Make sure your CMOS battery is good by examining your setup parameters, shutting down and
turning off your computer for ten minutes, then going into Setup again. If your CMOS is
not retaining changes, you will need to replace the battery. Many modern systems will
display a warning at start up that the CMOS battery is getting low.
|
|
If changes you make to your CMOS Setup are not saved after rebooting:
- Check to make sure that you are exiting the CMOS routine properly. Often the default
exit will not include a "Save."
|
|
|
| Video Problems
If your computer appears to be starting normally but you see no video activity:
- Make sure your monitor is plugged in and turned on.
- Make sure your monitor is working by trying it on a known, good, working system.
- Make sure your monitor's cable is securely seated in the video board slot.
- Make sure your video card is securely seated in its expansion slot.
- Try a known, good, monitor. If it does not work, you may need to replace your video
card.
|
|
 |
 |
| Back: Introduction |
Next: Hard Drive Problems |
|
