Shahid Ayub
December 05, 2014
0
Motherboards
The most important part of any
computer is the motherboard. As the name implies a motherboard is the mother of
all other components in a computer.
The motherboard brings all the core
components together such as the Central Processing Unit (CPU), Memory and Hard
Disks. In short, the motherboard connects and allows all of the components in
the computer to work together.
There are two different types of
Motherboard: AT style and ATX style.
AT
Motherboards
The AT-style motherboards represent
the classic approach to component placement. AT-motherboards are available in
two variations, the baby AT and the full AT. Both variations simply refer to
the overall dimensions of the board.
AT Boards are generally found in
older systems, typically those that use the now aged Pentium Processor. The
Majority of AT motherboards had a single keyboard port soldered to the
motherboard
The I/O ports (e.g. USB, COM and
PS/2 ports) are separate from the motherboard and are placed on a riser card or
separate headers.
To identify an AT motherboard first
check the power connectors. AT Motherboards use two sets of 6-pin inline power
connectors
Caution it is possible to plug these
connectors in the wrong order and fuse the motherboard
ATX
Motherboards
The ATX-style motherboards are a
result of the industry’s push for standardization and are found in most systems
today. Most modern computers contain an ATX motherboard. ATX boards can use
Advanced Power Management.
Distinguished by having more than
just one external connector ATX boards have Keyboard, Mouse, Serial, Parallel
and USB connectors.
ATX boards can also be distinguished
by the monoblock power connectors. Also available in micro ATX enabling the use
of smaller cases.
Motherboard
Components
There are two types of receivers for
CPU’s
Zero insertion force or ZIF sockets.
With a ZIF socket, before the CPU is inserted, a lever or slider on the side of
the socket is moved, pushing all the sprung contacts apart so that the CPU can
be inserted with very little force (generally the weight of the CPU itself is
sufficient with no external downward force required). The lever is then moved
back, allowing the contacts to close and grip the pins of the CPU, often with a
fan attached for cooling.
Single Edged Contact (SEC) cartridge
slot or Slot 1 seen on PII and PIIIs. Developed by Intel to add Cache memory
for the processor cheaply. The processor is mounted on a Single Edge Connector
Cartridge (SECC), much like a PCI slot, but with a 242-lead edge-connector.
Bridges
There are two main bridges on a
motherboard the Northbridge and the Southbridge. Bridges control access to the
processor from the peripherals.
The Northbridge, also known as the
Memory Controller Hub (MCH), is traditionally one of the two chips in the core
logic chipset on a PC motherboard. The Northbridge typically controls
communications between the CPU, RAM, AGP or PCI Express, and the Southbridge..
A Northbridge will typically work with only one or two classes of CPUs and
generally only one type of RAM. There are a few chipsets that support two types
of RAM (generally these are available when there is a shift to a new standard).
The Southbridge, also known as the
I/O Controller Hub (ICH), is a chip that implements the “slower” capabilities
of the motherboard in a Northbridge Southbridge chipset computer architecture.
The Southbridge can usually be distinguished from the Northbridge by not being
directly connected to the CPU. Rather, the Northbridge ties the Southbridge to
the CPU. The functionality found on a contemporary Southbridge includes:PCI
bus, ISA bus, SMBus, DMA controller, Interrupt controller, IDE, (SATA or PATA)
controller ,LPC Bridge, Real Time Clock, Power management (APM and ACPI) and
Nonvolatile BIOS memory
BIOS
Chips
The [[BIOS( Basic Input Output
System)]] refers to the software code run by a computer when first powered on.
The primary function of BIOS is to prepare the machine so other software
programs stored on various media (such as hard drives, floppies, and CDs) can
load, execute, and assume control of the computer. This process is known as
booting up.
The BIOS is stored as a ROM
(Read-Only Memory) program and is retained when the machine is turned off.
Settings within the BIOS may be changed by the user and these changes are
stored in the BIOS memory this is maintained by a trickle of charge from the
BIOS battery.
Memory
SIMMS- Single Inline Memory Modules.
An older type of memory only seen on very old motherboards came in 30 pin
modules and 72 pin modules.
SDRAM chips are rated according to
their maximum clock rate and their read cycle time. Common clock ratings
include 66MHz, 100MHz, and 133MHz. Common read cycle times include 50ns and
60ns.
DDR SDRAM or double-data-rate
synchronous dynamic random access memory is a type of memory integrated circuit
used in computers. It achieves greater bandwidth than ordinary SDRAM by
transferring data on both the rising and falling edges of the clock signal
(double pumped). This effectively nearly doubles the transfer rate without
increasing the frequency of the front side bus.
Stick/module specification
PC-1600: DDR-SDRAM memory module specified to operate at 100 MHz using DDR-200 chips, 1.600 GByte/s bandwidth
PC-2100: DDR-SDRAM memory module specified to operate at 133 MHz using DDR-266 chips, 2.133 GByte/s bandwidth
PC-2700: DDR-SDRAM memory module specified to operate at 166 MHz using DDR-333 chips, 2.667 GByte/s bandwidth
PC-3200: DDR-SDRAM memory module specified to operate at 200 MHz using DDR-400 chips, 3.200 GByte/s bandwidth
PC-1600: DDR-SDRAM memory module specified to operate at 100 MHz using DDR-200 chips, 1.600 GByte/s bandwidth
PC-2100: DDR-SDRAM memory module specified to operate at 133 MHz using DDR-266 chips, 2.133 GByte/s bandwidth
PC-2700: DDR-SDRAM memory module specified to operate at 166 MHz using DDR-333 chips, 2.667 GByte/s bandwidth
PC-3200: DDR-SDRAM memory module specified to operate at 200 MHz using DDR-400 chips, 3.200 GByte/s bandwidth
Drive
Connectors
Integrated Device Electronic (IDE)
[Integrated Device Electronic
(IDE)]] connectors connect the motherboard, via a ribbon cable to various
peripherals, the most common being hard drives and CD ROMs. On most boards
there are 2 channels/connectors, each can have 2 devices attached giving a
total of four IDE devices.
If one device is attached to a
cable, it should be configured as the master. If two devices are attached to
the same cable then one must be the master device and one the slave. Master and
slave are configured by the use of jumpers. Jumpers are small, insulated
sleeves with a contact inside used to complete a circuit
Hard
Disks
Hard disks are used to store data in
a non-volatile form within the machine. I.e. the data remains intact even if
the power to the device is cut off. Data is stored as magnetic ones and zeros
on a steel platen and is read by pickup arms that scan the drive as the platens
spin
Most major hard drive and
motherboard vendors now support self-monitoring, analysis, and reporting
technology (S.M.A.R.T.), by which impending failures can be predicted, allowing
the user to be alerted to prevent data loss.The mostly sealed enclosure
protects the drive internals from dust, condensation, and other sources of
contamination. The hard disk’s read-write heads fly on an air bearing which is
a cushion of air only nanometers above the disk surface. The disk surface and
the drive’s internal environment must therefore be kept immaculate to prevent
damage from fingerprints, hair, dust, smoke particles, etc., given the
submicroscopic gap between the heads and disk.
Floppy
Disks
The floppy disc controller is
generally situated near the IDE controllers and in fact looks like a small IDE
slot
The ribbon has a twist and the first
floppy drive (A: drive) should be placed after the twist if the cable has more
than three connectors. If the cable is really old it may have a connector for a
5 1/4 Floppy drive.
SCSI
SCSI stands for “Small Computer
System Interface”, and is a standard interface and command set for transferring
data between devices on both internal and external computer buses. SCSI is most
commonly used for hard disks and tape storage devices, but also connects a wide
range of other devices, including scanners, printers, CD-ROM drives, CD
recorders, and DVD drives. In fact, the entire SCSI standard promotes device
independence, which means that theoretically SCSI can be used with any type of
computer hardware.
On a parallel SCSI bus, a device
(e.g. host adapter, disk drive) is identified by a “SCSI ID”, which is a number
in the range 0-7 on a narrow bus and in the range 0-15 on a wide bus.
SATA
Serial ATA (SATA) is a computer bus
technology primarily designed for transfer of data to and from a hard disk. It
is the successor to the legacy AT Attachment standard (ATA). This older
technology was retroactively renamed Parallel ATA (PATA) to distinguish it from
Serial ATA. Both SATA and PATA drives are IDE (Integrated Drive Electronics)
drives, although IDE is often misused to indicate PATA drives.
The two SATA interfaces, SATA/150,
runs at 1.5 GHz resulting in an actual data transfer rate of 1.2 Gigabits per
second (Gb/s), or 150 megabytes per second (MB/s). SATA II 3Gb/s resulting in
an actual data transfer rate of 2.4 Gb/s, or 300 MB/s.
Motherboard
Slots
To add more functionality to a
computer, cards such as network or video cards can be added. Sometimes these
functions are built into the motherboard. There are several types of expansion
slots:
The PCI (Peripheral Component
Interconnect) The PCI bus is common in modern PCs, where it has displaced ISA
as the standard expansion bus, but it also appears in many other computer
types.
PCI 2 33.33 MHz clock with synchronous transfers peak transfer rate of 133 MB per second for 32-bit bus
PCI 2.2 allows for 66 MHz signalling (requires 3.3 volt signalling) (peak transfer rate of 503 MB/s) PCI 2.3 permitted use of 3.3 volt and universal keying, but did not support 5 volt keyed add in cards.
PCI 3.0 is the final official standard of the bus, completely removing 5 volt support.
PCI 2 33.33 MHz clock with synchronous transfers peak transfer rate of 133 MB per second for 32-bit bus
PCI 2.2 allows for 66 MHz signalling (requires 3.3 volt signalling) (peak transfer rate of 503 MB/s) PCI 2.3 permitted use of 3.3 volt and universal keying, but did not support 5 volt keyed add in cards.
PCI 3.0 is the final official standard of the bus, completely removing 5 volt support.
ISA/EISA; Industry Standard
Architecture and Extended Industry Standard Architecture An older type of bus
connector. Considered obsolete
PCI Express, PCIe, or PCI-E is an
implementation of the PCI computer bus that uses existing PCI programming
concepts, but bases it on a completely different and much faster serial
physical-layer communications protocol. PCIe transfers data at 250 MB/s (238
MiB/s), per channel to a maximum of 16 channels, a total combined transfer rate
of 4GB/s (3.7 GiB/s). Almost all of the high end graphics cards being released
today use PCI Express. NVIDIA uses the high-speed data transfer of PCIe for its
newly developed Scalable Link Interface (SLI) technology, which allows two
graphics cards of the same chipset and model number to be run at the same time,
allowing increased performance.
The Accelerated Graphics Port (also
called Advanced Graphics Port) is a high-speed point-to-point channel for
attaching a graphics card to a computer’s motherboard, primarily to assist in
the acceleration of 3D computer graphics. Some motherboards have been built
with multiple independent AGP slots. AGP is slowly being phased out in favour
of PCI Express.
AGP 1x, using a 32-bit channel
operating at 66 MHz resulting in a maximum data rate of 266 megabytes per
second (MB/s), doubled from the 133 MB/s transfer rate of PCI bus 33 MHz /
32-bit; 3.3 V signaling.
AGP 2x, using a 32-bit channel operating at 66 MHz double pumped to an effective 133 MHz resulting in a maximum data rate of 533 MB/s; signaling voltages the same as AGP 1x;
AGP 4x, using a 32-bit channel operating at 66 MHz quad pumped to an effective 266 MHz resulting in a maximum data rate of 1066 MB/s (1 GB/s); 1.5 V signaling;
AGP 8x, using a 32-bit channel operating at 66 MHz, strobing eight times per clock, delivering an effective 533 MHz resulting in a maximum data rate of 2133 MB/s (2 GB/s); 0.8 V signaling.
AGP 2x, using a 32-bit channel operating at 66 MHz double pumped to an effective 133 MHz resulting in a maximum data rate of 533 MB/s; signaling voltages the same as AGP 1x;
AGP 4x, using a 32-bit channel operating at 66 MHz quad pumped to an effective 266 MHz resulting in a maximum data rate of 1066 MB/s (1 GB/s); 1.5 V signaling;
AGP 8x, using a 32-bit channel operating at 66 MHz, strobing eight times per clock, delivering an effective 533 MHz resulting in a maximum data rate of 2133 MB/s (2 GB/s); 0.8 V signaling.
Peripheral
Connections
There are a number of ports on the
motherboard for the connection of additional devices:.
Serial ports connected the computer
to devices such as terminals or modems. Mice, keyboards, and other peripheral
devices also connected in this way.
Parallel ports are most often used
to communicate with peripheral devices. The most common kind of parallel port
is a printer port, such as a Centronics connector based port which transfers
eight bits at a time. Disk drives are also connected via special parallel
ports, such as those used by the SCSI and ATA technlogies. However, when people
refer to a parallel port, they are usually referring to a printer port, either
on a printer or a PC.
A USB system has an asymmetric
design, consisting of a host controller and multiple daisy-chained devices.
Additional USB hubs may be included in the chain, allowing branching into a
tree structure, subject to a limit of 5 levels of branching per controller. No
more than 127 devices, including the bus devices, may be connected to a single
host controller. Modern computers often have several host controllers, allowing
a very large number of USB devices to be connected. USB cables do not need to
be terminated.
USB supports three data rates.
A Low Speed rate of 1.5 Mbit/s (183 KiB/s) that is mostly used for Human Interface Devices (HID) such as keyboards, mice, and joysticks.
A Full Speed rate of 12 Mbit/s (1.5 MiB/s). Full Speed was the fastest rate before the USB 2.0 specification and many devices fall back to Full Speed. Full Speed devices divide the USB bandwidth between them in a first-come first-served basis and it is not uncommon to run out of bandwidth with several isochronous devices. All USB Hubs support Full Speed.
A Hi-Speed rate of 480 Mbit/s (57 MiB/s).
A Low Speed rate of 1.5 Mbit/s (183 KiB/s) that is mostly used for Human Interface Devices (HID) such as keyboards, mice, and joysticks.
A Full Speed rate of 12 Mbit/s (1.5 MiB/s). Full Speed was the fastest rate before the USB 2.0 specification and many devices fall back to Full Speed. Full Speed devices divide the USB bandwidth between them in a first-come first-served basis and it is not uncommon to run out of bandwidth with several isochronous devices. All USB Hubs support Full Speed.
A Hi-Speed rate of 480 Mbit/s (57 MiB/s).
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