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 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.

The control unit coordinates activities inside the processor. 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 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 16- bit 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, 32- bit 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