Motherboard Largest circuit board inside the computer which contains the CPU , memory(RAM,ROM) and various support chips for the CPU and expansion slots to connect smaller circuit board to interface different devices such as monitor , printer , sound card with computer.

Motherboard components

Expansion slots The Expansion slots are long thin connectors on

the computer , near the back side of the computer

Various cards are connected to the motherboard through data, address , control lines/buses on the slots.

Expansion bus and card

Expansion buses are connected to different expansion card through the expansion slots on the motherboard.

A new devices can be connected to your computer using these expansion card.

BUS

Bus is an electronic path on which signals are sent from one part of the computer to another

Data Bus:- Data bus is set of wire or tracks on the motherboard .Used to transfer data from one point to another . No of data lines determine the speed of data transfer

Address Bus:- Address bus is set of wire or tracks on the motherboard which is used to specify address of memory location.

Types of Buses on motherboard

• ISA

• EISA

• PCI

• PCI-X

• AGP

• Processor Bus

• PCI Express

Buses on motherboard

8 bit ISA

• Eight Data lines

• Four DMA channels

• Eight IRQ levels

• Enable to handle 1MB of memory.

8 Bit ISA

• Advantages

• It supports old type of cards

• low cost

• Disadvantages

• It is slower

• Supports 8 bit devices only

• Not suitable for modern PCs

• Jumpers & DIP switches.

16 bit ISA(AT with 286 processor.)

• Eight more data lines.

• Four more address lines

• Four more DMA channels

• Five IRQ levels.

• Old 8-bit cards

16 Bit ISA

Advantages

• Supports 16 bit CPU

• Compatible with old 8 bit cards

• low cost

• Disadvantages

• Not suitable for modern PCs

• low speed

• Jumpers & DIP switches.

EISA(32 bit) • 32 bit data path

• Enough address lines for 4GB of memory.

• More I/O address up to 64 kb.

• No jumper or DIP switches.

• 8 Mhz clock rate.

• Support 8 bit ,16 bit ISA cards

• Bus mastering.

Advantages • Support 8 bit and 16 bit ISA cards.

• Bus Mastering

• No jumper or DIP switches.

• Address up to 4 GB.

• Support 8 bit ,16 bit ISA cards

• Support 64kb I/O addresses.

• EISA permits greater system expansion with fewer adapter conflicts.

Disadvantages: It has two row of connector.

Can handle 32 bit data at an 8 Mhz clock rate.

Data transfer require min 2 cycles.

Less bandwidth support.

PCI (specifications)

• 32 bit High speed bus that connects high performance peripherals like video adapters, disk adapters and network adapters to the chipset.

• Processor independent

• Multi-master capability

• Plug and play facility :

PnP means that you can connect a device or insert a card into your computer and it is automatically recognized and configured to work in your system.

• 3.3 and 5 volt logic

• PCI 2.2, PCI 2.3, PCI 3.0

Features Of PCI bus. • Extremely high-speed data transfer.

• Plug and play facility.

• New approach

• Processor independence.

• Full multi-master capability.

• Parity on both data and address lines.

PCI 2.2 2.3,3.0,PCI-X.PXC-X 2.0 mini PCI

Card bus Compact PCI.

PCI-X • PCI-X is officially processor-independent.

• 64-bit parallel bus

• 1.5 Volts signaling level.

• PCI-X 1.0 doubled the maximum clock frequency that can be used by PCI devices from 66 MHz to 133Mhz

• PCI-X 2.0 supports maximum clock frequencies of 266 MHz and 533 MHz

• Theoretical Max. Transfer Rate4 Gbytes/sec

Comparison PCI and PCI-X

PCI Express (PCI-E) • PCI Express is a serial based technology. Each serial link is called

as a Lane. Every lane is fully duplex.

• High performance: Bandwidth increases as more lanes are added.

• I/O simplification: PCI-Express reduces the complexity of design and cost of implementation.

• Layered architecture–PCI Express establishes an architecture that can adapt to new technologies while preserving software investment.

• Next-generation I/O–PCI Express provides new capabilities for data acquisition and multimedia through isochronous data transfers.

• Ease of use–PCI Express offers both hot-swap and hot-plug.

• The PCI Express 1X connector has 36 pins and is intended for high-bandwidth I/O use

• The PCI Express 4X connector has 64 pins and is intended to be used on servers:

• The PCI Express 8X connector has 98 pins and is intended to be used on servers:

• The PCI Express 16X connector has 164 pins, is 89 mm long and is intended to be used on the graphics port:

PCI Express 1.0 In 2004, Intel introduced PCIe1.0, with a data rate of

250MB/s

PCI Express 2.0 T he PCIe2.0 standard doubles the per-lane throughput from

the PCIe1.0 standard's 250MB/s to 500MB/s

PCI Express 3.0 PCI Express 3.0 carry a data rate of 1 GB/Ss.

Key features of PCI Express

Compatibility with existing PCI enumeration and software device drivers.

Physical connection over copper, optical, or other physical media to

allow for future encoding schemes.

Maximum bandwidth per pin allows for small form factors, reduced cost, simpler board designs and routing, and reduced signal integrity issues.

Embedded clocking scheme enables easy frequency (speed) changes as compared to synchronous clocking.

Bandwidth (throughput) increases easily with frequency and width (lane) increases.

Low latency suitable for applications requiring isochronous (time-sensitive) data delivery, such as streaming video.

Hot-plugging and hot-swapping capabilities.

Power management capabilities.

AGP • The AGP interface was developed specifically to connect

with the video card bypassing the input-output controller.

• AGP is currently being phased out in favor of PCI Express

• The AGP bus is 32 bits wide and uses 66.66 MHz clock speed.

• Reduced contention

• The processor on the video adapter can directly access RAM on the motherboard when needed.

Advantages of AGP over PCI.

1.AGP is dedicated pathway between slot and processor, rather than sharing the PCI bus, allows faster communication.

2. AGP is capable of reading textures directly.

AGP Bus

Comparison AGP-PCI

Processor Bus (Front Side Bus)

• The processor bus is the communication pathway between the CPU and motherboard chipset—more specifically the North Bridge or Memory Controller Hub.

• This bus also transfers data between the CPU and external cache in Pentium class systems

• This bus runs at the full motherboard speed typically between 66 MHz to 800 MHz .

• To determine the transfer rate for the processor bus, you multiply the data width by the clock speed of the bus

Memory Memory is the place where computer stores the

program and data that help the program in carrying out its operations.

RAM:-Random access memory( volatile type, read/write)

ROM:-Read only memory (non-volatile type , read)

RAM

What is RAM?

Random Access Memory.

RAM is volatile.

Broadly classified as

Static RAM.

Dynamic RAM.

Static RAM Fast, has lower access time.

An array of flipflops.

Typical access times 5-25 ns.

Expensive.

Cache memory is Static RAM.

Dynamic RAM

Slower, has higher access time than Static RAM.

Made up of MOS transistor gates.

Stores data in the form of charge on the capacitor.

Typical access times 60-120 ns.

Much cheaper than SRAM.

Main Memory is Dynamic RAM.

Memory Bandwidth is proportional to System Bus speed.

Dynamic RAM are further classified as

SDRAM (Synchronous DRAM) : PC100, PC133.

It runs in synchronization with the memory bus and delivers data in high speed burst.

DDR SDRAM (Double Data Rate SDRAM)

It has twice data transfer rate than SDRAM.

The data is transferred two times per transfer cycle, once at the rising edge and once at the falling edge of clock signal.

These RAMS are available in DIMM modules with 184 pins and required 2.5 volts for operating.

DDR1 DDR2 DDR3

Supply Voltage 2.5 V 1.8 V 1.5 V

Cycle Time 6 – 10 ns 3 - 10 ns 5 – 10 ns

Bus Clock 100-200 Mhz 200-533 Mhz 400-1066 Mhz

Data Transfer/second 226-400 MT/s 533-800 MT/s 1066- 1600 MT/s

BIOS Basic Input Output System

The BIOS resides in a ROM

chip, which is mounted on the motherboard, usually in a socket so it is removable.

ROM BIOS –store important program such as application program and hardware such as floppy disk , hard disk, video adapter card etc communicate with each other

BIOS contain POST program

Power on self test –program check the motherboard and other devices connected to the computer during the system power on time

Functions of BIOS

Give instructions for POST.

HOW to interact with critical component such as drives and memory.

User can make adjustment to BIOS through a configuration screen.

Flash memory card to hold BIOS information.

Flash memory- New type of EEPROM that can be erased and reprogrammed using the normal operating voltage found inside the PC

What is it? - Basic Input Output System

Why is it necessary?

boot up

Important Functions

Check CMOS Set-up.

POST - Power On Self Test.

Display system setting.

Initiate bootstrap sequence.

Configuring BIOS

• • System Time/Date.

• • Boot Sequence.

• • Plug and Play.

• • Drive Configuration.

• • Security.

• • Power Management.

Coprocessor Coprocessor is special purpose microprocessor which is used to speed up main processor job by taking over some of the main processor’s work.

CPU • Central Processing Unit

• Main component of motherboard which controls all the inner function of the system.

• It is inserted into the socket

Supported chipset

• Conventional Memory

Reserved Area

Video RAM

UemoUser Programs)

User data and program

TSR program

Command.com

Interrupt Vector

Device drivers

DOS

A summary: Available to all PCs Limited to 640 KB Virtually every program can use this memory By default, device drivers, and TSRS load in conventional memory.

Conventional Memory • Bottom 1k area :: store interrupt vector pointers.

• Dos space : depends on DOS version

• Device Drivers

• Command.Com

• TSR ::Terminate and Stay Resident loaded from autoexec.bat

• User data and programs

UMA (upper memory area)

• Upper 384kb of first megabyte

• Use by system devices and ROM shadowing and drivers.

HMA

1. first 64kb of second megabyte.

2. can be used in real mode.

3. Used for DOS.

• Extended Memory

Extended Memory Reserved for BIOS

Reserved for display V RAM

Conventional Memory

A summary: Best for windows and multi-tasking operating system. Only possible with machines based on 286 and later chips; impossible with XTs. Used by OS/2, Unix, windows (3.X,95,98,and NT/2000/XP)

• Expanded memory

Extended Memory

Motherboard ROM BIOS

EMS Window

Adapter ROM

Video RAM

Conventional Memory

Expanded Memory

Divide into Logical Pages and Mapped into the EMS window

416 K pages (64 K) of “bank switched”, memory appear in the EMS window usually at the EMS segment

A summary: Also called LIM memory or EMS memory. Can be used with PCs, XTs or 8-bit systems – 386 and above can make their extended memory to expanded memory.

Extended memory • Memory above first MB.

• Above HMA until end of system memory.

• Used in protected mode

• Commonly used manager is HIMEM.sys

• (XMS) specification.

• Used in 80286 onwards.

• Developed by Microsoft Intel, AST Corp

• Best for windows and multitasking os.

• Used by OS/2, Unix, Windows(3.X,95,98,NT/2000/XP)

Expanded Memory • Older std. For accessing memory above 1MB.

• Used EMS protocol.

• Created to overcome of 1MB addressing limitations of first generation 8088 and 8086 cpu.

• System uses a free segment in the upper memory area as home address for the EMS board.

• After 64k is filled new empty segemnt appears to take its place.

CONCEPT OF CACHE MEMORY: • …Cache is a smaller, faster memory which stores copies

of the data from the most frequently used main memory locations.

• …When the processor needs to read from or write to a location in a main memory, it first checks whether a copy of that data is in the cache. If so, the processor immediately reads from or writes to the cache, which is much faster than reading from or writing to the main memory.

• …The CPU uses cache memory to store instructions that are repeatedly required to run programs, improving overall system speed.

• …The advantage of cache memory is that the CPU not has to use the motherboard’s system bus for data transfer. Whenever data must be passed through the system bus, the data transfer speed slows to the motherboard’s capability.

…

• As it happens, once most programs are open and running, they use very few resources. When these resources are kept in cache, programs can operate much quickly and efficiently.

LEVELS OF CACHE:

• Cache built into the CPU itself is referred to as level 1 (L1) cache.

• Cache that resides on a separate chip next to the CPU is called as level 2 (L2) cache.

• Some CPUs have both L1 and L2 cache built-in and designate cache chip as level 3(L3) cache.

• Level 1 (L1) (Internal Cache):

• L1 or primary cache is a small high speed cache incorporated right onto the processor’s chip.

• The L1 cache typically ranges in size from 8KB to 64 KB and uses high speed SRAM instead of slower and cheaper DRAM used for main memory.

• Level 2 (L2): • L2, or secondary cache, is a memory between the RAM and the CPU

(but not on the CPU chip itself) and is bigger than the primary cache (typically 64KB to 2MB).

• L2 ATC (Advanced Transfer Cache) uses micro-architectural improvements, which provide a higher data bandwidth interface between the L2 cache and the processor core and is completely scalable with the processor core frequency.

• It is also a unified, non-blocking cache which improves performance.

• L3 cache: • L3 cache is slowly replacing the L2 cache function and the extra cache

built into the motherboards between the CPU and the main memory (old L2 cache definition) is now being called the L3 cache.

• Some manufacturers have proprietary L3 cache designs already, but most desktops do not offer this feature yet.

• Micron has developed a chip set with 8MB of on-chip DRAM in the north bridge chip that acts an L3 cache, but offering an L3 cache as standard equipment is still a future aspect.

ADVANTAGES:

• Enhances the speed of system or improving performance.

• Reduces a traditional system bottleneck.

• The access time is very small.

• Instructions take less time to execute.

• Data transfer gets quicker.

• Cache memory is intelligent memory.

• It holds current working set of code and data.

• Reduces wait states.

DISADVANTAGES:

• Size is really small

• Cost is very high.

DETAILS OF OPERATION: • When processor needs to read from or write a location

in main memory, it refers to the cache first. • It is accomplished by comparing the address location

of all tags in the cache. • If found, we say a cache hit has occurred or else we

speak of a cache miss. • In case of cache hit, the processor immediately reads or

writes the data in the cache line. The proportion of access that results in a cache hit is known as the Hit rate and is a measure of the effectiveness of the cache.

• In case of a cache miss, most allocate a new memory, which compromises the tag just missed and a copy of the data from the memory.

• Misses are comparatively slow because they require the data to be transferred from the main memory.

Thanks