Wednesday, 21 May 2014


Diploma Engineering


Chapter 1

Chapter Details
1.1 Introduction
    Chipset Architecture
North/South Bridge Architecture
1.4 Buses on Motherboard(Expansion OR I/O Slot)
Hub Architecture
Intel Chipset 915G
Intel Chipset 945G


A computer is a programmable electronic device that can Store , retrieve and process data. The architecture of computer is the conceptual design and fundamental operational structure of a computer system, whereas computer maintenance is the practice of keeping computers in a good state. The basic structure of the computer is shown in fig. 1.1. Figure 1.1: Components of motherboard Based on these structures different Personal Computers (PCs) are designed. The different components and peripherals in a modern PC system are:

1. Motherboard
2. Processor
3. Memory (RAM/ROM)
4. Interface cards/daughter boards.
6. Hard disk drive
7. CD-ROM drive
8. Keyboard
9. Mouse
10. Monitor

Motherboard and Its Components

The most important component in any PC is the motherboard, also called as system board. It houses a microprocessor, memory and slots for expansion, of the system. Some motherboards also contain the drive interface logic, printer interface logic and serial interface logic integrated on it. Motherboard comes in different sizes, shapes and models. The height and width of the motherboard is known as motherboard form factor.

The main functional blocks of a motherboard are as follows:
i. CPU
ii. BIOS
iii. RAM
iv. Cache memory
v. Bus expansion slots
vi. On-board IO connectors
vii. On-board IDE connectors.
i. CPU:
 The Central Processing Unit (CPU) is the brain of the computer in which
majority of the computing tasks are performed. The CPU may have a heat sink
installed on it, to dissipate heat generated by the CPU.
ii. BIOS (Basic Input Output System):
 BIOS is a ROM chip. It contains programs that
are necessary for the PC to boot and to access the various system components.
BIOS also contains the programs for POST (Power On Self Test).
iii. RAM (Random Access Memory):
 RAM is used for storing programs temporarily.
Generally RAM is located on SIMM (Single Inline Memory Module) or DIMM
(Dual Inline Memory Module).
iv. Cache Memory:
 The cache is the fastest memory which lies between CPU and
RAM. The CPU can access the frequently required data from cache more rapidly
than from RAM.
v. Bus Expansion Slots/I/O Slots:
 System expansion is possible using the bus
expansion slots in which the adapters are installed. The different types of slots such
as ISA, VESA, PCI are available on motherboard.
vi. On-board I/O Connectors:
 In recent systems one or two serial ports (com1, com2)
and parallel ports (LPT1, LPT2) are present on motherboard.
vii. On-board IDE Connectors:
 Similar to serial and parallel parts the motherboard
may have IDE connectors for connecting. Floppy Disk Drives (FDD), Hard Disk
Drives (HDD) and CD Drives.


To reduce the number of chips on the motherboard, the logics around the processor are integrated into two or three chips. These chips work in conjunction with processor. These chips contain more than one logic like DMA logic, timer logic, interrupt logic and peripheral interface logic. Hence these chips are called as chipset. In PC, the chipset represents the connection between the processor and everything else. The processor can’t talk to the memory, adapter boards, devices without going through the chipset/ If processor is the brain, the chipset is spine and central nervous system of computer. The chipset manufacturers are Intel, Acer Labs, Silicon Integrated System (SIS) and AMD etc. To maximize performance of a motherboard picks up a proper microprocessor and a good chipset.

1.2.1 Chipset Architecture

Intel has used two different chipset architectures:
i. North/South bridge architecture
ii. Hub architecture.
All the chipsets introduced from the 800 series onwards, use the hub architecture.

1.2.2 North/South Bridge Architecture:

Most of Intel’s earlier chipsets are broken into a multi-tiered architecture, consisting North and South Bridge components as well as a Super I/O Chip. Fig. 1.2 shows North/South Bridge architecture. 1>The North Bridge: North bridge is the connection between the high-speed processor bus and the slower AGP and PCI buses. Sometimes, it is referred as the PAC (PCI/AGP Controller). It is the main component of the motherboard which is placed beside the processor. It runs at full motherboard (processor bus) speed. Chipset Most of the modern chipsets use a single chip North bridge, however older ones consist of up to three different chips. 2>The South Bridge: South bridge is the connection between the PCI bus and the slower ISA bus. It is the lower speed component in the chipset and has always been a single individual chip. The south bridge connects to the 33 MHz PCI bus and contains the interface or bridge to the 8 MHz ISA bus. It also contains dual IDE hard disk controller interfaces, one to two USB interfaces and even CMOS RAM and real-time clock functions. It contains all the components that make up the ISA bus, including the interrupt and DMA controllers. 3>The Super I/O Chip: It is connected to the 8 MHz ISA bus and contains all the standard peripherals that are built into a motherboard such as serial ports, parallel ports, floppy controller, keyboard and mouse interface. Some motherboards have a super south bridge containing south bridge and super I/O functions into a single chip. Figure 1.2: Architecture of north/south bridge-7

1.2.3 Hub Architecture

The newer chipsets from Intel use hub architecture. In hub architecturem, North bridge chip is called as Memory Controller Hub (MCH) and South bridge chip is called as I/O Controller Hub (ICH). Systems that include integrated graphics use a Graphics Memory Controller Hub (GMCH) instead of MCH. The standard South/North bridges are connected through PCI bus, but here they are connected via a dedicated hub interface that is at least twice as fast as PCI. This design allows a much greater throughput for PCI devices because there is no south bridge chip using the PCI bus. There are two main variations in the hub interface: i. AHA (Accelerated Hub Architecture): It is used by 8xx?series of chipsets. It has twice the throughput of PCI. ii. DMI (Direct Media Interface): It is used by 9xxand 3x series chipsets. DMI is basically a dedicated 4 bit wide PCI Express connection allowing 1 GBps in each direction. Following fig. 1.3 shows hub architecture: Figure 1.3: Hub architecture / architecture of Intel Chipset 915 G


As Intel develops new processor, it develops chipsets and motherboards simultaneously. Here we are going to study architecture of Intel chipset 915 G and 945 G.

1.3.1 Intel Chipset 915 G

The Intel 915 chipset family was introduced in 2004. This family has six members - 910 GL, 915 PL, 915 P, 915 G, 915 GV and 915 GL, all of which support the 90 mm Pentium-4 prescott core. These chipsets are the first to support the socket 775 processor interface. This chipset model support the Hyper Threading (HT) Technology feature built into most recent Pentium 4 processors. It supports bus speed upto 800 MHz. It supports dual channel DDR memory upto 400 MHz and PCI - Express X1 and PCI version 2.2 expansion slots. This also supports the new DDR2 memory standard at speed upto 533 MHz. The 915 G has a PCI express X16 slot as well as integrated Intel Graphics Media Accelerator 900. All 915 series MCH/GMCH chips use the new ICH6 family of South Bridge replacements.
Features of Intel 915 G Chipset (refer fig. 1.3)
1. Code Name              : Grandsdale - G
2. Port Number            : 828915 G
3. Bus Speeds             : 800 / 533 MHz
4. Supported Processor    : Pentium IV, Celeron, Celeron-D
5. SMP (dual CPUs)        : No
6. Memory Types           : DDR 333 / 400, Dual Channel DDR2
7. Maximum Memory         : 4GB
8. Memory banks           : 2
9. PCI Support            : PCI Expres-X1, X16, PCI 2.2
10. PCI Speed/Width       : 33MHz/32 bit
11. PCI Express X-16 Video: Yes
12. AGP slot              : No
13. Integrated Video      : Extreme Graphics 3
14.South Bridge (Hub): ICH6 family-9

1.3.2 Intel Chipset 945 G

The Intel 945 Express Chipset family was released in 2005. It includes 3 members 945 G, 945 P and 945 PL. This chipset is the first to support Intel’s new dual core Pentium D processors. It also supports Pentium-4 Hyper Threading (HT) Technology processors using socket 775. The 945 G is aimed as the ‘Performance PC’. It offers Front Side Bus (FSB) speed up to 1,066 MHz. It supports up to 4GB of dual-channel DDR2 memory (2 pairs) running at upto 667 MHz. It features PCI Express X16 support and also incorporates Intel Graphics Media Accelerator 950 integrated graphics. All members of the 945 family support the ICH7 family of I/O controller hub chips. The ICH7 family differs from ICH6 in the following ways: i. It has support for 300 MBps serial ATA. ii. It has support for SATA RAID 5 and Matrix RAID. iii. It has support for two additional PCI-Express X1 ports.
Features of Intel 945 G Chipset
1. Code Name              : Lakeport GG
2. Port Number            : 82945 G
3. Bus Speed              : 1066 / 800 / 533 MHz
4. Supported Processors   : Pentium-D, Pentium-4 with HT Technology
5. SMP (Dual CPUs)        : No
6. Memory Types           : DDR2 667/533/400 MHz dual channel DDR2
7. Maximum Memory         : 4GB
8. Memory banks           : 2
9. PCI Support            : PCI Expres-X1, X16, PCI 2.3
10. PCI Speed/Width       : 33MHz/32 bit
11. PCI Express X-16 Video: Yes
12. AGP slot              : No
13. Integrated Video      : GMA 900
14. South Bridge (Hub)    : ICH7 family
Figure 1.4: Architecture of Intel Chipset 945 G


The heart of any motherboard is the various buses that carry signals between the components. Bus is a group of wires through which the CPU communicates with memory, coprocessor, keyboard and other ICs in the motherboard. The PC has a hierarchy of different buses as the processor bus and I/O buses. The processor bus is also called as Front Side Bus (FSB). It is the communication pathway between the CPU and motherboard chipset. This bus runs at the full motherboard speed. 1-11 The I/O bus enables your CPU to communicate with peripheral devices. It enables you to add devices to your computer to expand its capabilities.

The different I/O buses on motherboard are as follows:
i. ISA                        ii. PCI-X
iii. PCI-Xpress               iv. PCMCIA
v. AGP                        vi. Processor Bus (FSB)

1.4.1 ISA (Industry Standard Architecture)

ISA is the 8 bit bus architecture that was used in IBM-PC in 1981. It was later expanded to 16 bits. It is a very slow speed bus which is ideal for certain slow speed or older peripherals such as plug-in modems, sound cards etc.

Features of 8 bit ISA Bus
i. It provides 8 data lines.
ii. It has four DMA channels.
iii. It has eight IRQ levels.
iv. 20 addressing lines.
v. 8 bit ISA slot handles 1 MB of memory.
vi. 8 bit version ran at 4.77 MHz
vii. It provides Bandwidth 4.17 MBps.
Features of 16 bits ISA Bus
It was introduced as 16 bit ISA bus used in IBM PC/AT in 1984.
i. It has 16 data lines.
ii. 24 address lines
iii. 8-DMA channels
iv. Interrupt requests
v. Backward compatible with 8 bit TSA bus.
vi. Ran at 8.33 MHz.
vii. Bandwidth 8.33 MBps

1.4.2 EISA (Extended ISA)

This architecture support 32 bit buses with much higher data transfer rates upto 33 MBps. It provides backward compatibility to 8 bit and 16 bit ISA cards. 1-

i. 32 bit data bus
ii. It handles 4GB of memory.
iii. 8.33 MHz clock speed
iv. Bandwidth 33 MBps
v. Backward compatible with 8 bit and 16 bit ISA cards.
vi. Support 64 kB T10 addresses.
1.4.3 PCI (Peripheral Component Interconnect) : PCI is the acronym for Peripheral Component Interconnect. It is a high speed bus that connects high performance peripherals like video adapters, drive adapters and network adapters to the chipset, processor and memory. PCI bypasses the standard I10 bus. IT uses the system bus to increase the bus clock speed and take full advantage of the CPUs data path. The most recent motherboards usually provide 4 or 5 PCI slots. The 1 PCT bus can be either 32 bits or 64 bits wide. Information is transferred across the bus at 33 MHz and 32 bits at a time. The Bandwidth is 133 MBps. PCI with 64 bits of 66.66 MHz provides bandwidth 533 MBps. These variations are used only on server or workstation types boards.

>1.4.4 PCI-X (Peripheral Component Interconnect Extended)

It is standard designed computer bus or expansion slot advanced to PCI. PCI-X is faster version of PCI running at twice the speed of PCI. PCI-X was developed by IBM, HP and Compaq. PCI X doubles the clock speed from 66 MHz to 133 MHz and hence amount of data exchanged between the computer processor and peripherals. Standard PCI supports up to 64 bit at 66 MHz.