CertiGuide to A+ (A+ 4 Real)  9  Chapter 8: Motherboards

What is BIOS? 1 What is a Bus?

POST stands for Power On Self Test. The POST involves both CMOS and BIOS components so we will tie in some of the concepts you have already learned into this section.

When a computer is first powered on, the operating system has not yet loaded. The operating system is the program that provides the primary interface that allows a person to interact with the computer hardware, utilities and application software. Before the operating system is loaded, the computer requires instruction of what to do including a systems test to check for device functioning. In most cases, no error is found, the POST completes, the remainder of the boot process finishes, and the operating system loads. Most users are almost completely unaware of what has just occurred.

Let’s say for a moment that an error is found. How does the computer signal the user? I message on the monitor would be fine…except if the monitor or video card were the components malfunctioning. A series of “beep codes” are programmed to alert the user of a problem before and during video testing (after the video tests out fine, alerts are sent to the monitor). The most common beep code error is two beeps, which indicate a problem with the RAM. Unfortunately, beep codes are not always specific and as a technician, you will have to investigate the problem by powering down the machine and opening up the box. A common problem here is that a RAM stick has become loose and simply needs to be reseated into its slot.

What is BIOS? 1 What is a Bus?