Chapter 9 Motherboard

Seite 1

In this chapter, you will learn

how to

■ Explain how motherboards work

■ Recognize modern expansion

buses

■ Upgrade and install

motherboards

■ Troubleshoot motherboard problems

The motherboard contains the wires—

called traces—that make up the buses of the system

ATX Form Factor

The microATX (μATX) motherboard (see

Figure 9.10) floats in at a svelte 9.6 by 9.6

FlexATX

motherboards have maximum dimensions of

just 9 by 7.5 inches, which makes them the

smallest motherboards in the ATX standard

Mini-ITX is the largest and the most popular

of the three ITX form factors. At a miniscule 6.7

by 6.7 inches,

If you think that’s small, Nano-ITX at 4.7

by 4.7 inches and

Pico-ITX at 3.8 by 2.8 inches

Chipset The Northbridge chip on traditional Intel-based

motherboards helped the CPU work with RAM, as

mentioned in earlier chapters. On newer motherboards,

however, the CPU has taken on the role of the memory

controller so the Northbridge either no longer exists or

mainly just provides the communication with the video

card. Northbridge chips did a lot and thus got pretty hot, requiring their

own heat-sink and fan assembly

The Southbridge handles some expansion devices and mass storage

drives, such as hard drives. Most Southbridge chips don’t need extra cooling,

leaving the chip exposed or passively cooled with only a heat sink. This

makes the Southbridge a great place for you to see the manufacturer of the

chipset, as the name of the manufacturer is always right on the chip.

Chipset makers don’t always use the terms Northbridge

and Southbridge. Chipsets for AMD-based motherboards

tend to use these terms, but Intel-based motherboards

tend to say Memory Controller Hub (MCH) for the

Northbridge and I/O Controller Hub (ICH) for the Southbridge.

Motherboard Components

RAID

RAID stands for redundant array of independent (or inexpensive) disks and is

very common on motherboards. There are many types of RAID, but the

RAID found on motherboards usually only supports mirroring (the process

of using two drives to hold the same data, which is good for safety, because

if one drive dies, the other still has all of the data) or striping (making two

drives act as one drive by spreading data across them, which is good for

speed). RAID is a very cool but complex topic that’s discussed in detail in

Chapter 11.

Clock crystals aren’t just for CPUs

and chipsets. Pretty much every chip in

your computer has a CLK wire and needs

to be pushed by a clock chip, including

the chips on your expansion cards. Suppose

you buy a device that did not come

with your computer—say, a sound card.

The chips on the sound card need to be

pushed by a CLK signal from a crystal. expansion bus crystal. The expansion slots run at a much slower speed than the frontside bus.

The chipset acts as the divider between the two buses, compensating for

the speed difference with wait states and special buffering (storage) areas.

No matter how fast the motherboard runs, the expansion slots run at a standard

speed.

PCI Intel introduced the Peripheral Component Interconnect (PCI) bus architecture

(see Figure 9.26) in the early 1990s,

PCI in its many new forms is still “King of the Motherboard.”

Accelerated Graphics Port (AGP).

PCI-X

PCI Extended (PCI-X) is a huge enhancement to PCI that is also fully backward

compatible in terms of both hardware and software. PCI-X is a 64-bitwide

bus (see Figure 9.28). The obvious candidates for PCI-X are

businesses using workstations and servers,

because they have the “need for speed” and

also the need for backward compatibility.

Mini-PCI format

(see Figure 9.29). You’ll find Mini-PCI in just about every

laptop these days. Mini-PCI is designed to use low power

and to lie flat

PCI Express PCI Express (PCIe)

PCI Express

PCI Express (PCIe) is the latest, fastest, and most popular expansion

bus in use today. As its name implies, PCI Express is still

PCI, but it uses a point-to-point serial connection instead of

PCI’s shared parallel communication. Consider a single 32-bit

chunk of data moving from a device to the CPU. In PCI parallel

communication, 32 wires each carry one bit of that chunk

There was a 64-bit version of

the original PCI standard, but it

was quite rare.

The AGP slot is almost

universally brown in color,

making it easy to spot.

• Figure 9.27 AGP slot

• Figure 9.29 Tiny card in Mini-PCI slot. See the contacts

at the bottom of the picture?

• Figure9.28 PCI-X slot

Mike Meyer’s CompTIA A+ Guide to Managing and Troubleshooting PCs 276

/ Mike Meyers’ CompTIA A+ Guide to Managing and Troubleshooting PCs, Fourth Edition / Meyers / 591-X / Chapter 9

of data. In serial communication, only one wire carries those 32 bits. You’d

think that 32 wires are better than one, correct? Well, first of all, PCIe doesn’t

share the bus. A PCIe device has its own direct connection (a point-to-point

connection) to the Northbridge, so it does not wait for other devices. Plus,

when you start going really fast (think gigabits per second), getting all 32

bits of data to go from one device to another at the same time is difficult,

because some bits get there slightly faster than others. That means you need

some serious, high-speed checking of the data when it arrives to verify that

it’s all there and in good shape. Serial data doesn’t have this problem, as all

of the bits arrive one after the other in a single stream. When data is really

going fast, a single point-to-point serial connection is faster than a shared

32-wire parallel connection

Installing Expansion Cards

You install any of

them using the same four steps:

1 knowledge,

2 physical installation,

3 device drivers, and

4 verification.

Always unplug the PC before inserting an expansion

card! Failure to do so can destroy the card, the motherboard,

or both. It’s not worth the risk.

Step 3: Device Drivers

You know from Chapter 8 that all devices, whether built into the motherboard

or added along the way, require BIOS. For almost all expansion

cards, that BIOS comes in the form of device drivers—software support programs

Unsigned Drivers :::::: Microsoft truly

wants your computer to work, so

they provide an excellent and rigorous

testing program for hardware

manufacturers called the Windows

Certification Program. Developers

initially use software to test their

devices and, when they’re ready,

submit the device for further testing.

Hardware and drivers that

survive the testing get to wear the

Designed for Windows logo. The drivers

get a digital signature that says

Microsoft tested them and found all

was well.---------------that says you’re about to install an unsigned driver.

The fact that a company refuses to use the Windows Certification Program

doesn’t mean their drivers are bad—it simply means they haven’t

gone through Microsoft’s exhaustive quality-assurance certification procedure

Upgrading and Installing MOBO's

First, determine what motherboard you need. What CPU are you using?

Will the motherboard work with that CPU? Because most of us buy the

CPU and the motherboard at the same time, make the seller guarantee that

the CPU will work with the motherboard. If you can, choose a motherboard

that works with much higher speeds than the CPU you can afford; that way you can upgrade later. How much RAM do you intend to install? Are extra

RAM sockets available for future upgrades?

Third, all motherboards come with a technical manual, better known

as the motherboard book (see Figure 9.45). You must have this book!

Unscrew the motherboard. It will not simply lift out. The motherboard

mounts to the case via small connectors called standouts that

slide into keyed slots or screw into the bottom of the case (see Figure 9.48).

With a catastrophic failure, the PC just won’t boot.

This sort of problem happens to brand-new systems because of manufacturing

defects—often called a burn-in failure—and to any system that

gets a shock of electrostatic discharge

Component failure happens rarely and appears as flaky connections

between a device and motherboard, or as intermittent problems

This three-part system—check, replace, verify good component—works

for both simple and more complicated motherboard problems. You can even

apply the same technique to ethereal-type problems that might be anything,

but you should add one more verb: document

Once you determine that the motherboard has problems, you have several

options for fixing the three types of failures. If you have a catastrophic failure,

you must replace the motherboard. Even if it works somewhat, don’t

mess around. The motherboard should provide bedrock stability for the

system. If it’s even remotely buggy or problematic, get rid of it!

If you have a component failure, you can often replace the component

with an add-on card that will be as good as or better than the failed device.

Adaptec, for example, makes fine cards that can replace the built-in SATA

ports on the motherboard (see Figure 9.51).

If your component failure is more a technology issue than physical damage,

you can try upgrading the BIOS on the motherboard. As you’ll recall

from Chapter 8 on BIOS, every motherboard comes with a small set of code

that enables the CPU to communicate properly with the devices built into

the motherboard. You can quite readily upgrade this programming by flashing

the BIOS: running a small command-line program to write new BIOS in

the flash ROM chip. Refer to Chapter 8 for the details on flashing.

Finally, if you have an ethereal, ghost-in-the-machine type of problem

that you have determined to be motherboard related, you have only a couple

of options for fixing the problem. You can flash the BIOS in a desperate

attempt to correct whatever it is, which sometimes works and is less expensive

than the other option, which is replacing the motherboard.

Limits of BIOS

Upgrades

Flashing the BIOS for a

motherboard can fix a lot of

system stability problems and

provide better implementation

of built-in technology. What it

cannot do for your system is

improve the hardware.