Datasheet

Identifying Motherboards 39
If you make a mistake in the upgrade process, the computer can become
unbootable. If this happens, your only option may be to ship the box to a
manufacturer-approved service center. Be careful!
Post Routines
Every computer has a diagnostic program built into its BIOS called the power-on self-test
(POST). When you turn on the computer, it executes this set of diagnostics. Many steps
are involved the POST, but they happen very quickly, they’re invisible to the user, and they
vary among BIOS versions. The steps include checking the CPU, checking the RAM, check-
ing for the presence of a video card, and so on. The main reason to be aware of the POST’s
existence is that if it encounters a problem, the boot process stops. Being able to determine
at what point the problem occurred can help you troubleshoot.
One way to determine the source of a problem is to listen for a beep code. This is a series of
beeps from the computer’s speaker. The number, duration, and pattern of the beeps can some-
times tell you what component is causing the problem. However, the beeps differ depending
on the BIOS manufacturer and version, so you must look up the beep code in a chart for your
particular BIOS. Different BIOS manufacturers use the beeping differently. AMI BIOS, for
example, relies on a raw number of beeps, and uses patterns of short and long beeps.
Another way to determine a problem during the POST routine is to use a POST card.
This is a circuit board that fits into an ISA or PCI expansion slot in the motherboard and
reports numeric codes as the boot process progresses. Each of those codes corresponds to a
particular component being checked. If the POST card stops at a certain number, you can
look up that number in the manual that came with the card to determine the problem.
BIOS Central is a website containing charts detailing the beep codes and
POST error codes for many different BIOS manufacturers:
www.iterasi
.net/openviewer.aspx?sqrlitid=px8b_zkg9eiiv-n5ilfowq
.
Bus Architecture and Slots
A bus is a set of signal pathways that allows information and signals to travel between
components inside or outside a computer. A motherboard has several buses, each with its
own speed and width.
The external data bus, also called the system bus, connects the CPU to the chipset. On
modern systems, it’s 64-bit. The address bus connects the RAM to the CPU. On modern
systems, it’s 64-bit.
The expansion bus connects the I/O ports and expansion slots to the chipset. There
are usually several different expansion buses on a motherboard. Expansion buses can be
broken into two broad categories: internal and external. Internal expansion buses include
Industry Standard Architecture (ISA), Peripheral Component Interconnect (PCI), and
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