On the Motherboard
Chapter 2
Objectives
• After completing this chapter you will be able to
▫ Define the purpose of the major components on a
motherboard including the BIOS, clock, front side bus,
and expansion slots
▫ Explain the basic operation of a processor and what
issues must be considered when upgrading it
▫ Recognize and identify the motherboard, CPU, and
expansion slots
▫ Compare and contrast motherboard expansion slots
▫ Identify methods to add functionality to portable
devices
Processor Overview
• At the heart of every computer is a special
motherboard chip called the processor that
determines, to a great extent, the power of the
computer.
• The processor is also called the CPU (central
processing unit) or microprocessor.
• The major processor manufacturers today are Intel,
Motorola, VIA, and AMD (Advanced Micro
Devices, Inc.). The processors designed by Motorola
have been used in Apple computers for years.
Processor Basics
• All processors use 1s and 0s. One 1 or one 0 is a
bit.
• Eight bits grouped together are a byte.
• The letter A looks like 01000001 to the
processor.
• Each character on a keyboard appears as one
byte or eight bits to the processor.
• Microprocessors come in a variety of speeds. The
speed of processors is measured in gigahertz
(GHz).
▫ Hertz is a measurement of cycles per second.
▫ One hertz equals one cycle per second.
▫ One gigahertz is one billion cycles per second or 1GHz.
• The number of bits processed at one time is the
microprocessor’s register size (word size).
▫ Register size is in multiples of 8 bits (i.e., 8-, 16-, 32-,
64-, or 128-bit).
• The 1s and 0s must travel from one place to
another inside the processor as well as outside to
other chips.
• To move the 1s and 0s around, electronic lines
called a bus are used.
• The electronic lines inside the CPU are known as
the internal data bus or system bus.
• For the CPU to communicate with devices in the
outside world, such as a printer, the 1s and 0s
travel on the external data bus.
• Processors have a special component called the ALU
(arithmetic logic unit), which does all the calculations
and comparison logic needed by the computer.
▫ Today’s processors actually have two ALUs
• The control unit coordinates activities inside the
processor.
• The I/O unit manages data entering and leaving the
processor.
• The registers within the CPU are a very high speed
storage area for 1s and 0s before the bits are processed.
• Processors have multiple pipelines (separate internal
buses) that operate simultaneously.
Cache
• Cache memory is a very fast type of memory
designed to increase the speed of CPU operations.
• When cache memory is integrated as part of the
CPU, it is called L1 cache. Included in the
processor packaging,
• but not part of the CPU is L2 cache, which some
refer to as on-die cache.
• Finally, there is a third level of memory found when
using higher end server processors called L3 cache,
which can be located in the CPU housing or on the
motherboard.
Clocking
• The motherboard generates a clock signal that is
used to control the transfer of 1s and 0s to the
CPU.
• Processor clock timing signals go as fast as 100,
133, 166, 200, 266, or 333 MHz (millions of
cycles per second).
• A clock signal can be illustrated as a sine wave.
• One clock cycle is from one point on the sine
wave to the next point that is located on the
same point on the sine wave later in time, as
shown in Figure 2.5.
• In older computers, data was sent to the CPU
only once during a clock cycle. Then, newer
memory technologies evolved that allow data to
be sent twice during every clock cycle.
• Today, data is sent four times during a single
clock cycle, as shown in Figure 2.6.
• The back side bus connects the CPU to the L2
cache.
• The FSB (front side bus) connects the CPU to the
motherboard components.
• The FSB is considered the speed of the
motherboard. Figure 2.7 illustrates the concept
of a front side bus.
Multi-Core Processors
• Another way to speed up operations is to have two or more
processors.
• A dual-core CPU combines two CPUs in a single unit. Both
Intel and AMD offer dual-core processors.
• AMD offers a tri-core CPU, which has three processors in a
single unit.
• Both Intel and AMD have quad-core CPU technologies,
which is either two dual-core CPUs installed on the same
motherboard (Intel’s solution) or two dual-core CPUs
installed in a single socket (AMD and Intel solution).
▫ Intel and AMD’s dual and quad core technologies are different,
especially in regard to how the CPU accesses L2 cache memory
and motherboard RAM.
• AMD core processors directly access RAM on the
motherboard, and each core has its own L2
cache and, optionally, L3 cache.
• Intel processors share L2 cache and access RAM
via an external memory controller or have an
integrated memory controller within the CPU
packaging.
Sockets and Slots
• A processor inserts into a socket or slot depending on the
model.
• There are different types of sockets:
▫ PGA (pin grid array), which has even rows of holes around the
square socket;
▫ SPGA (staggered pin array), which has staggered holes so more
pins can be inserted;
▫ PPGA (plastic pin grid array) used on Intel Celerons and Pentium
4s;
▫ μPGA (micro pin grid array) used by AMD; and
▫ LGA (land grid array) used with AMD and Intel processors.
• Figure 2.11 shows a LGA775 socket (also called a Socket T).
• The processor sockets used today are called ZIF sockets
(zero insertion force)
Processor Cooling
• In today’s systems the fans and heat sinks are very
large.
• A heat sink looks like metal bars protruding from
the processor.
• Some systems have multiple fans to keep the CPU
cool.
▫ Figure 2.12 shows a fan and a heat sink.
• Additional motherboard components can also have
heat sinks attached.
▫ These are normally the chipset and/or the I/O
(Input/Output) controller chips.
▫ Figure 2.13 shows a motherboard with these cooling
elements.
Overclocking Processors
• Overclocking is changing the front side bus speed and/or
multiplier to boost CPU and system speed. Before
describing the overclocking steps, we must discuss the
issues.
▫ Because the CPU is normally covered with a heat sink
and/or fan, you cannot easily tell the CPU speed. Be wary of
vendors who sell a system advertised with a higher rated
CPU speed than what is installed.
▫ CPU speed ratings are conservative.
▫ The CPU, motherboard, memory, and other components
can be damaged by overclocking.
▫ Applications may crash, the operating system may not boot,
and/or the system may hang when overclocking.
▫ The warranty is void on most CPUs if you overclock.
▫ When you increase the speed of the CPU, the
processor’s heat increases. Extra cooling by fans and
larger heat sinks are essential.
▫ PCI and SCSI devices may not react well to
overclocking.
▫ The hard drive PIO mode may need to be changed
because of overclocking.
▫ The memory chips may need to be upgraded to be able
to keep up with the faster CPU.
▫ Know how to reset the system BIOS in case the
computer will not pass POST after making changes.
Expansion Slots
• An expansion slot is used to add an adapter to the
motherboard, and it has rules that control how many bits can
be transferred at a time to the adapter, what signals are sent
over the adapter’s gold connectors, as well as how the adapter
is configured. Figure 2.17 shows expansion slots on a
motherboard.
• Expansion slots used in PCs are usually some form of PCI
(peripheral component interconnect) or AGP (accelerated
graphics port).
• Other types of expansion slots that have been included with
older PCs are ISA (industry standard architecture), EISA
(extended industry standard architecture), MCA (micro
channel architecture), and VL-bus (sometimes called VESA
[video electronics standards association] bus).
ISA (Industry Standard Architecture)
• ISA is the oldest expansion slot. ISA allows 16bit transfers to adapters installed in ISA slots.
• The number of expansion slots available
depends on the motherboard manufacturer.
• Because computer manufacturers want
customers to be able to use their old adapters in
an upgraded motherboard or a new computer,
ISA is still available on the market.
PCI (Peripheral Component
Interconnect)
• A previously popular expansion slot is PCI
(peripheral component interconnect) bus.
• PCI comes in four varieties: 32-bit 33MHz, 32bit 66MHz, 64-bit 33MHz, and 64-bit 66MHz.
• Figure 2.18 shows the most common type of PCI
expansion slot.
AGP (Accelerated Graphics Port)
• AGP (accelerated graphics port) is a bus
interface for graphics adapters developed from
the PCI bus.
PCIe (Peripheral Component
Interconnect Express)
• PCI, PCI-X, and AGP are being replaced with PCIe
(PCI Express), which is also seen as PCI-E.
• PCIe is better than the other types of PCI expansion
slots.
• The older PCI standard is half-duplex bidirectional,
which means that data is sent to and from the PCI or
PCI-X card, but in only one direction at a time.
• PCIe sends data full-duplex bidirectionally; in other
words, it can send and receive at the same time.
• Figure 2.23 shows this concept.
Chipsets
• The principle chips on the motherboard that
work in conjunction with the processor are
known as a chipset.
• Usually a chipset goes with a particular
processor and determines which memory chips a
motherboard can have.
• Chipsets determine a lot about what a
motherboard can allow or support.
Types of Motherboards
• Motherboards come in different sizes known as
form factors.
• The most common motherboard is ATX.
• The different types of ATX are known as
microATX (sometimes shown as μATX),
miniATX, FlexATX, EATX, WATX, miniATX,
nanoATX, picoATX, and mobileATX.
• Older form factors include AT, baby AT, NLX, LPX,
and miniLPX.
• Some motherboards, such as the NLX and LPX form
factors, had a riser board that attached to the
smaller motherboard.
The end