What Happens When You Start’er UP? -

The Power-On-Self-Test (POST)

Now that you know about the 10…or 11 main parts of a modern computer system, you need to know how they work together.

When any computer first boots up, it performs a POST (Power On Self Test) or system check. Basically, a POST check allows a computer to count all its “fingers and toes” and make sure all the ten parts listed earlier are online and active.

If anything goes wrong during the POST check, the computer will signal an error (a possible part failure) via a series of “beeping” sounds or with a text message on the monitor if the video/graphic card is working.

The Power on Self Test (POST)

1. The Power Supply is turned on via the power-on button on the case.
2. The BIOS is triggered. The BIOS (basic input/output system) is pronounced “bye-ose”. It is a very basic software program (most are mutations from the first IBM BIOS from 1981) and it is installed at the factory on chip on the motherboard.
3. Imagine if you will, the BIOS as a traffic cop manually directing how each device comes up and making sure that all the other chips, drives, ports and CPU all flow together without crashing.
4. The BIOS tests itself. (If this fails the game is pretty much over).
5. The BIOS tests the Power Supply Unit and makes sure it’s online and able to send a steady energy signal to the rest of the motherboard.
6. The CPU is powered on and made active.
7. Next, the CMOS is started and “read”. Pronounced “see-moss”, these CMOS chips store the date, time, any system passwords and other system settings. They are powered by a battery when the computer is turned off.
8. The BIOS tests all memory chips and RAM sticks. If the first 64K of RAM is bad or unreadable, the BIOS will create an error message and the POST will stop with an error beep.
9. Find, initialize and organize all devices that are available for boot up. The BIOS signals that all is well internally with a final “All Systems Go” beep.
10. The BIOS then turns on the video card. This displays the motherboard & memory test information on screen. You may also see a manufacturer’s logo flash on the screen.
11. It then does a keyboard and mouse test. This is one test where you can watch as your keyboard’s lights blink on or off. A keyboard failure will be shown on screen.
12. Next the hard drive, floppy and CD/DVDs are tested and booted up. You will hear and see the drive lights wink on and off. A hardware (hard drive or CD/DVD) failure will be shown on screen.
13. The POST check is complete and the BIOS hands everything off the main Operating System software.

Okay so how does this POST cycle help you?

During any part of the testing cycle (which takes only a couple of seconds by the way) if something doesn’t work, the computer will give you an audible error signal. In other words, if something bad happens your computer will “beep” at you.

The original BIOS or POST beep codes were first developed by IBM. Today most beep codes are installed by each motherboard manufacturer. While each manufacturer may modify codes for their own testing purposes, most vendors maintain a fairly standard set of codes.

Here are some of the most common PC beep codes:

• 1 short beep – Normal POST – No problems detected
• No beep – no power, power supply, motherboard problem, disconnected CPU, loose card or disconnected speaker
• Continuous beep – Power supply, motherboard, or keyboard problem
• Repeating short beeps – Power supply or motherboard or keyboard
• Repeating long beeps – RAM (memory stick) is unseated
• 1 long, 1 short beep – Motherboard problem
• 1 long, 2 short beeps – Video Card, Video Card Slot
• 1 long, 3 short beeps – Video Card, Video Card Slot
• 3 long Beeps – keyboard or keyboard port (motherboard problem)
• 1 beep, Blank or Incorrect Display – Monitor, Video Card, Video Card Slot

See by watching and “listening” to what your computer is telling you, you will have a jump on any major hardware problems just by powering on your PC.

Under The Hood – The 10 “Moving” Parts of a Computer

Despite what anyone tells you, troubleshooting a desktop computer is usually a very straightforward thing.

There are just 10 “moving” parts to a standard desktop or tower PC. A laptop has exactly the same parts (if you exclude the “built-in” screen, keyboard and glidepad)only miniaturized and squeezed into a much smaller case.

The Ten Parts

1. Motherboard, system or mainboard. This is a big circuit board with various “slots” and “sockets” that holds the rest of the parts.

2. CPU or “central processor unit” is the main “chip” inside. It’s the brain of the computer.

3. RAM or “Random Access Memory” comes in “sticks”. RAM acts data holding tanks for the CPU. The more RAM the a computer has; the faster it can operate. Is a view of the RAM installed in a computer.

Expansion Cards is any type of computer circuit card that inserted into the motherboard. This may include Video or Graphic, Sound, Network or Modem.

4. Audio or Sound card. Most modern units have an “onboard” system (see motherboard picture above) that is built into the motherboard. However, replacement and upgrade cards are available.

5. Video or Graphic card. Like sound cards, most computers have “onboard” systems that are built-in. But replacement and upgrade cards are available for special functions like high power video games or digitally record your favorite TV shows like a Tivo.

6. Modem cards (not to be confused with cable modems) are still used for dial-up Internet connections but are slowly being replaced with faster DSL and broadband connections.

7. Network cards are for all Ethernet(wired networks) or broadband and DSL Internet connections (either high-speed cable or phone lines). These cards are part of any wired network.

8. The Hard Drive is the central storage unit for computer. It holds operating systems, motherboard/card software (drivers), applications and other programs. Here is an image of a hard drive in a computer case.

9. CD/DVD Drives have become the primary “removable” storage devices replacing the venerable floppy drive.

10. Floppy Drives, while being phased out, have been the standard since the beginning of personal computers. Many models still use them as the secondary boot device.

Here is an image of floppy drives down thru history

From left to right:
• Qume D/T 8, 8 inch drive, 1.2 MB. Made in 1980.
• Tandon TM 100-2A , 5 1/4 inch drive, 360 KB. Made in 1983.
• Sony MPF920, 3 1/2 inch drive, 1.4 MB. Made in 2004.

11. Case and Power Supply Unit. So, I said ten, but from my point of view, a good power supply unit or PSU and case are some of the most important components in a computer.

A failing power supply unit the computer simply will not boot or run improperly damaging other devices. Your motherboard or CPU may burn out sooner than expected or suffer power fluctuations.

• a. You can see the Power Supply Unit at the back of the case: it’s the “fan” where the main power cord outlet is set. The PSU has two main jobs: provide juice to all the components inside the case and use its’ fan to keep things cool.
• b. The “Case” is usually the “white box” or “black box” or “grey box” everything sets in. Some cases are simple to open. Still others are like trying to untie a Gordian knot. And laptops should only be opened with instructions from repair professionals.
• c. Cables are the most often “forgotten” part in a PC. The multi-color power cables connect the power supply unit to the motherboard and other devices. And while the flat grey data cables run from the motherboard to the floppy, CD/DVD, hard drives

See, I told you, just ten simple, little parts. Well maybe a bit more than ten but most of which you already knew about or have used.

By understanding the basic functions of those parts and applying a little common sense with a wee bit of how-to knowledge, you can effectively uncover and fix most of the problems that are plaguing your PC.