Day Three
Motherboards and their components
A+ Certification
Core and DOS/WINDOWS
Objectives.
CORE refers to questions that pertain to PC hardware
DOS/WINDOWS refers to questions that pertain to software issues.
Study guides can be found HERE
A+ Guide to
Managing and Maintaining Your PC, Third Edition, Comprehensive
4th Edition
Jean Andrews
Published by Course
Technology
© 2001
ISBN/ISSN: 0-619-00038-4
MEASURE
PREP20
A+ Test Preparation from Thomson Learning
http://www.geocities.com/aplus_practice_exams/index.htm
DAY THREE
Class notes
Motherboard and Components
System Boards
A system boards may also
be called a planar board, motherboard or main board. There are various types of
system boards that differ depending on the type of case that they fit in and
the type of processor that they host. The form factor of the motherboard
describes its general shape, what sorts of cases and power supplies it can use
and its physical layout. A company can make 2 motherboards that have basically
the same functionality but that use a different form factor and the only real
differences will be the physical layout of the board and the position of the
components. Common form factors include AT, Baby AT, ATX, Mini ATX, LPX, Mini
LPX and NLX. The table below contains more information:
|
Style |
Where Found |
Match to Case and
Power Supply |
|
Full AT |
Very Old PCs |
Full AT, Full Tower |
|
Baby AT |
Older PCs |
All but Slimline,
ATX |
|
ATX |
Newer PCs |
ATX |
|
Mini ATX |
Newer PCs |
ATX |
|
LPX |
Older Retail PCs |
Slimline |
|
Mini LPX |
Older Retail PCs |
Slimline |
|
NLX |
Newer Retail PCs |
Slimline |
ATX, Socket 7 motherboard
ATX, Socket A motherboard
Motherboards also contain configurable jumpers and possibly even DIP switches. Jumpers use BERG pins and a small connector that slides onto the pins to designate "on". BERG connectors are also used to connect the front panel LEDs and switches to the board.
The back of the motherboard contains ports used for connecting various peripherals.
Peripherals are composed of input and output devices including the mouse,
keyboard, monitor, speakers, printer, etc. So what is the difference between
an input device and an output device? It is just as the name says. The mouse
and keyboard are input devices since they are used to provide the computer
with information. Output devices provide YOU with information such as speakers,
printers and the monitor. Older PC-XT and AT board typically had a 5 pin DIN
keyboard connection. The newer ATX style uses the smaller 6 pin mini DIN connection.
Expansion Busses:
|
Name |
Bit Size |
Notes |
|
ISA |
16 bit |
Older-Slower Bus
Type, works at 8 MHz
|
|
PCI |
32 bit |
Supports PnP, Burst Mode,
Bus Mastering. Utilizes the host bridge to communicate with other types of
expansion slots. |
|
AGP |
64 bit |
Variation of PCI designed
to handle 3D graphics better from video cards. |
Modern motherboards contain just
the AGP and PCI slots.
On newer and faster buses, a great deal of information is flowing through
the channel every second. Normally, the processor is required to control the
transfer of this information. Bus mastering involves having capable devices
take control of the bus and do the work themselves instead of utilizing the
CPU.
Plug-and-Play(PnP) - Compatible BIOSes can autodetect devices and assign resources
to them. Non PnP compatible devices are configured first followed by PnP devices.
The IRQ(interrupt request) value is an assigned location where the computer
can expect a particular device to interrupt it when the device sends the computer
signals about its operation.
Input/output(I/O) addresses are
resources used by virtually every device in a computer and represent locations
in memory that are designated for use by various devices to exchange
information between themselves and the rest of the PC. The following is a list
of common I/O settings.
1FO-1F8 - Hard Drive Controller, 16-bit ISA
220 - Soundcard
278-27F - LPT2
2F8-2FF - COM2
320-32F - Hard Drive Controller, 8-bit ISA
378-37F - LPT1
3D0-3DF - Video Adapter
3F0-3F7 - Floppy Controller
3F8-3FF - COM1
Universal Serial Bus (USB) - A high-speed I/O bus that supports the daisy
chaining of devices (up to 127). USB hubs are used to provide connections for
multiple devices. USB supports the addition and removal of devices while they
are on (hot-swapping). Devices are either full speed or low speed. Full speed
device cabling can be up to 16 feet 5 inches (5 meters) in length. Low speed
cabling is limited to 9 feet 10 inches (3 meters). USB supports Isochroous
transfers that can stream data such as voice or video.
System boards should all have:
CPU (Central Processing Unit)
System battery
Bus controller and connector
Memory
Expansion slots
Power supply connectors (AT or
ATX)
Keyboard connector
Basic Input/Output System
(BIOS)
Older motherboards were of the AT
design. This design created a large board
(12” wide by 13.8” deep), which would not fit into today’s smaller cases. Later
the baby AT came out, which was smaller.
They both used the large round 5-pin DIN keyboard connector.
In 1995, Intel introduced the ATX
design motherboard, which was smaller, used less energy, had added features,
and could support built-in video, audio, and network compatibilities. These boards could also support full-length
adapter cards.
Further notes on
COMPONENTS
CPU
The CPU or microprocessor is
made up of 10s of millions of transistors that enable the CPU to calculate and
process incoming data. Changes in current flow are responsible for performing
software instructions. Transistor size matters a great deal. Smaller
transistors means that more can be placed on a chip, giving greater
performance, yet using less energy.
There are two main types of
CPUs, CISC and RISC. CISC stands for Complex Instruction Set. RISC stands for Reduced Instruction
Set. CISC processors are used in
Windows based machines. RISC processors
are found in MAC based systems.
All CPUs have the following:
A primary storage unit to store
data and instructions while the computer is processing. One or more ALUs, Arithmetic/logic Units to
perform logic. A control unit, which
supervises all activities and data flow from RAM to the ALU. A processor socket, which is a grid of small
holes, which hold the CPU to the motherboard, like a ZIF (zero insertion force)
socket. A cooling fan is needed to
maintain a cool working environment.
BUSES
A bus is a pathway from the CPU
to the Adapter cards, which allows data to from the CPU to these other devices. They are like tiny highways, which electrons
drive on to carry data from one place to another.
System Bus- this carries the control signals, which
directs activity.
Address Bus- this carries the
memory locations (addresses), allowing to CPU to recall stored memories (data).
Data Bus- this carries data from
the CPU to the other devices, such as the monitor, modem, and printer.
BIOS
The Basic Input/Output System
is a set of instructions, which are stored on “READ-ONLY” chips. They perform three basic operations. 1) Configure the system hardware to turn on
and work. 2) Locates the operating System (OS) and allows that OS to control
the hardware. 3) Stays resident in the background as a type of interface
between the user and the OS.
Input/Output Addresses
I/O addresses allow devices to
communicate with the CPU as mailbox address allows us to send letters to each
other’s homes. But here data takes
the place of the letters. Each device
must have a unique address, if not, a conflict will occur and data will not
be sent to the correct device. Here
is a list of I/O address for common devices;
Common
Devices Address
|
COM1 |
3F8-3FF |
|
COM2 |
2F8-2FF |
|
LPT1 |
378-37F |
|
LPT2 |
278-27F |
|
XT, CONTROLLER |
320-32F |
|
FLOPPY CONTROLLER |
3F0-3F7 |
|
EGA/VGA |
3C0-3CF |
|
CGA |
3D0-3DF |
|
MONOCHROME |
3B0-3BF |
Direct memory access (DMA -
Channel)
This is memory that can be
accessed without going though the processor.
Devices, which use DMA are normally Hard Disk Drives and CD- ROMs. Here is a list of DMA channels for common
assignments;
Assignment DMA
|
Unassigned |
DMA 0 |
|
Sound Card |
DMA 1 |
|
FDD Controller |
DMA 2 |
|
Parallel Port |
DMA 3 |
|
Serial Port |
DMA 4 |
|
Unassigned, or sound, or SCSI |
DMA 5 |
|
Unassigned |
DMA 6 |
|
Unassigned |
DMA 7 |
Interrupt Request (IRQ) levels
IRQs are signals from devices
to the processor. When a device needs
to call the processor, it uses an IRQ to do so. When the processor hears a device called it, it will stop working
on what it was doing and receive the call from the device. Every device must have a unique IRQ, just like
we must have a unique phone number. IRQs
are numbered from 0 to 15
Assignment
IRQ
|
TIMER |
0 |
|
Keyboard |
1 |
|
Secondary Interrupt
Controller |
2 |
|
Serial Port 2 (COM 2) |
3 |
|
Serial Port 1 (COM 1) |
4 |
|
LPT2 or sound card |
5 |
|
Diskette Drive |
6 |
|
LPT 1 Parallel Port |
7 |
|
Real Time Clock |
8 |
|
IRQ 2 Redirected |
9 |
|
Often is the sound card |
10 |
|
PCI BUS or SCSI |
11 |
|
PS/2 Mouse |
12 |
|
Math Coprocessor |
13 |
|
Primary IDE (HDD) Controller |
14 |
|
Secondary IDE Controller |
15 |
Performance Issues
The CPU’s performance is based
on it’s speed and word size. Speed
is measured in Megahertz and Gigahertz. Word size is based on the amount of
bits that can be processes at one time. This
number is 16 bits for the older CPUs (8086, 286, some 386s) 32 bits for 486s,
and later CPUs.
Variables in CPU performance
CLOCK SPEED- which is the
number of cycles the CPU can perform per second. Internal Clock speed refers to the rate at which the processor
obtains information from within the CPU.
External Clock speed refers to the rate at which the CPU communicates
with the external components, such as memory (RAM).
MICROCODE- The instruction set
for the CPU. Complex Instruction Set
Computing for windows machines and Reduced Instruction Set Computing for Mac
machines.
Data Path Size- This is the largest
number a bus can transport at one time (8, 16, 32, 64, 128, 256 bits)
Internal Cache Memory- This is
memory is found within the CPU. It
normally runs at CPU speed, and therefore the CPU does not have to wait for
data stored in this memory.
External Cache Memory- This memory is found outside of the
CPU, but is still very fast. Common
sizes are from 128 KB to 4 MB.
Power Supply
Every Computer must have a
working power supply, which takes AC voltage from the wall outlet and converts
it to DC voltage. Undersize power
supplies can be a source for many problems including insatiability.
The “POWER GOOD SIGNAL” is a
signal sent to the motherboard if all is well.
After receiving this signal the motherboard begins to boot-up the
system. If the voltages are not within
acceptable levels, the system shuts down quickly as to prevent damage. These
processes take only a millisecond or two and cannot be observed by the user.
Voltages Used
|
+5 (RED) |
+12 (YELLOW) |
-5 (WHITE) , -12 (BLUE) |
+3.3 |
1.6 |
|
Motherboard |
Hard Disk Drive Motors |
Unused |
Pentium Classic CPUs |
Pentium III CPUs |
|
Most circuits on peripheral
cards |
ISA adapter cards |
|
|
|
|
|
Some High Speed Fans |
|
|
|
|
(+2.4 to +5.2) |
(+8.5 to +12.6) |
(-4.5 to –5.4) and (-8.5 to –12.6) |
|
|
Time/date not working
Boot-up failures
Spontaneous rebooting
Lockups under normal conditions
Memory errors
HDD and fans cannot work at
same time
Overheating
System resets
Electric shocks
Static discharges
Error messages with 01x or 02x
Intermittent system failures
Fan failures
Flickering LEDs
If the power supply sends a
power surge (a spike in voltage and current) the motherboard tries to protect
itself by activating a crowbar circuit that blows the power supply’s fuse.
Replace the power supply at this point.
AT and ATX differences
Portable computer Power
Supplies
Nickel Cadmium
Used for older systems
Nickel Metal Hydride
Better than Nickel Cadmium, but
has some disadvantages.
Lithium Ion
Today’s Standard. Long lasting and is more durable. Do not place Lithium Ion batteries in
systems that take older types of batteries or large amount of heat and energy
will be discharge, causing a fire!
Fuel Cell
Newer technology is shrinking the size of these devices for the use in portable PCs.
Motherboard and power supply
connectors
AT
Wire
Number
Connector ONE Connector TWO
|
1 |
Power Good |
Ground |
|
2 |
+5 |
Ground |
|
3 |
+12 |
-5 |
|
4 |
-12 |
+5 |
|
5 |
Ground |
+5 |
|
6 |
Ground |
+5 |
ATX
|
Wire Number |
Signal |
|
1 |
+3.3 |
|
2 |
+3.3 |
|
3 |
Ground |
|
4 |
+5 |
|
5 |
Ground |
|
6 |
+5 |
|
7 |
Ground |
|
8 |
Power Good |
|
9 |
+5 STANDBY |
|
10 |
+12 |
|
11 |
+3.3 |
|
12 |
-12 |
|
13 |
Ground |
|
14 |
Power on |
|
15 |
Ground |
|
16 |
Ground |
|
17 |
Ground |
|
18 |
-5 |
|
19 |
+5 |
|
20 |
+5 |
Power Protection
Many areas in the United States have power supplies, which can send a spike (over voltage for a nanosecond to microsecond) or a surge (over voltage for a millisecond or longer). These can fry any electronic device like a TV, radio, microwave oven, or a computer. An under voltage of power can be called a sag (a very short period of under voltage) a brownout (a prolonged period of under voltage) or a blackout (complete lose of power).
How can we protect our systems?
USE SURGE SUPPRESSERS with
A high joule rating (above 200)
Let-through voltage (UL 1449)
Line noise filter
Never plug a surge suppresser
into another surge suppresser.
A surge protect cannot protect your PC from brownouts.
PROTECT your system from surges from the phone line as well by using a modem surge protector.
UPS or Uninterruptible Power supply
These can maintain power for a few minutes even when there is no power from the wall outlet.
A UPS can protect your system from surges as well as brown outs or black outs.
~ACTIVITY~
Students introduce themselves in preparation of group formation.
Do be sure to include computer expertise and in which field.
