SAMPLE CHAPTER 1
THE FOLLOWING COMPTIA A+ ESSENTIALS EXAM OBJECTIVES ARE COVERED IN THIS CHAPTER: ia l 1 Personal Computer System Components M at er Chapter Ûß 1.2 Explain motherboard components, types and features Nß Nß ATX / BTX, Nß micro ATX Nß NLX I/O interfaces Nß C op yr ig ht ed Nß Form Factor 86498book.indb 1 Nß Sound Nß Video Nß USB 1.1 and 2.
Nß Nß Bus slots Nß PCI Nß AGP Nß PCIe Nß AMR Nß CNR Nß PCMCIA Chipsets BIOS / CMOS / Firmware Nß POST Nß CMOS battery Nß Riser card / daughterboard Nß [Additional subobjectives covered in chapter 2] Ûß 1.4 Explain the purpose and characteristics of CPUs and their features Nß Identify CPU types Nß AMD Nß Intel Nß Hyper threading Nß Multi core Nß Nß Dual core Nß Triple core Nß Quad core Onchip cache Nß L1 Nß L2 Nß Speed (real vs. actual) Nß 32 bit vs. 64 bit Ûß 1.
Nß Liquid cooling systems Nß Thermal compound Ûß 1.6 Compare and contrast memory types, characteristics and their purpose Nß 86498book.indb 3 Types Nß DRAM Nß SRAM Nß SDRAM Nß DDR / DDR2 / DDR3 Nß RAMBUS Nß Parity vs. Non-parity Nß ECC vs. non-ECC Nß Single sided vs. double sided Nß Single channel vs.
A personal computer (PC) is a computing device made up of many distinct electronic components that all function together in order to accomplish some useful task (such as adding up the numbers in a spreadsheet or helping you write a letter). Note that this definition describes a computer as having many distinct parts that work together. Most computers today are modular. That is, they have components that can be removed and replaced with a component of similar function in order to improve performance.
Identifying Components of Motherboards F I G U R E 1 .1 5 A typical system board Types of System Boards There are two major types of system boards: Nonintegrated system board Each major assembly is installed in the computer as an expansion card. The major assemblies we’re talking about are items like the video circuitry, disk controllers, and accessories. Nonintegrated system boards can be easily identified because each expansion slot is usually occupied by one of these components.
6 Chapter 1 N Personal Computer System Components With integrated system boards, there is a way around having to replace the whole motherboard when a single component breaks. On some motherboards, you can disable the malfunctioning onboard component (for example, the sound circuitry) and simply add an expansion card to replace its functions. System Board Form Factors System boards are also classified by their form factor (design): ATX, micro ATX, BTX, or NLX (and variants of these).
Identifying Components of Motherboards F I G U R E 1. 2 7 Both sides of a riser card with daughterboard LPX, a technology that lacked formal standardization and whose riser card interfaces varied from vendor to vendor, enjoyed great success in the 1990s until the advent of the Pentium II processor and the Accelerated Graphics Port (AGP). These two technologies placed a spotlight on how inadequate LPX was at cooling and accommodating high pin counts.
8 Chapter 1 N Personal Computer System Components Balanced Technology Extended (BTX) In 2003, Intel announced its design for a new motherboard, slated to hit the market mid- to late-2004. When that time came, the new BTX motherboard was met with mixed reactions. (Let’s postpone accusations of acronym reverse-engineering until “CTX” is announced as the name of the next generation.
Identifying Components of Motherboards Nß Peripheral ports and connectors Nß BIOS Nß CMOS battery Nß Jumpers and DIP switches Nß Firmware 9 In this subsection, you will learn about the most-used components of a motherboard, what they do, and where they are located on the motherboard. We’ll show what each component looks like so you can identify it on most any motherboard you run across. Note, however, that this is just a brief introduction to the internal structures of a computer.
10 Chapter 1 N Personal Computer System Components The term bus is also used in any parallel or bit-serial wiring implementation where multiple devices can be attached at the same time in parallel or in series (daisy-chained). Examples include Universal Serial Bus (USB), Small Computer System Interface (SCSI), and Ethernet. Chipsets A chipset is a collection of chips or circuits that perform interface and peripheral functions for the processor.
Identifying Components of Motherboards 11 Southbridge The Southbridge subset of the chipset, as mentioned earlier, is responsible for providing support to the myriad onboard slower peripherals (PS/2, Parallel, IDE, and so on), managing their communications with the rest of the computer and the resources given to them. These components do not need to keep up with the external clock of the CPU and do not represent a bottleneck in the overall performance of the system.
Chapter 1 12 N Personal Computer System Components Figure 1.5 shows a schematic of a typical motherboard chipset (both Northbridge and Southbridge) and the components they interface with. Notice which components interface with which parts of the chipset. F I G U R E 1.
Identifying Components of Motherboards 13 you might wish to research these slots for your own edification and to be prepared, should you find yourself face to face with such a beast in the field. PC Card buses, such as PCMCIA, are related more to laptops than to desktop computers and are covered in Chapter 4. PCI Expansion Slots Many computers in force today contain 32-bit Peripheral Component Interconnect (PCI) slots.
14 Chapter 1 F I G U R E 1.7 N Personal Computer System Components An AGP slot compared to a PCI slot PCI slot AGP slot AGP performance is based on the original specification, known as AGP 1x. It uses a 32-bit (4-byte) channel and a 66MHz clock, resulting in a data rate of 266.67MBps. AGP 2x, 4x, and 8x specifications multiply the 66MHz clock they receive to increase throughput linearly.
Identifying Components of Motherboards 15 on the number of lanes supported, which requires a related number of wires. Therefore, a x8 slot is longer than a x1 slot but shorter than a x16 slot. Every PCIe slot has a 22-pin portion in common toward the rear of the motherboard, which you can see in Figure 1.8, which orients the rear of the motherboard to the left. These 22 pins comprise mostly voltage and ground leads. There are three major versions of PCIe currently specified, 1.x, 2.0, and 3.0.
16 Chapter 1 F I G U R E 1. 8 N Personal Computer System Components PCIe expansion slots AMR Expansion Slots As is always the case, Intel and other manufacturers are constantly looking for ways to improve the production process. One lengthy process that would often slow down the production of motherboards with integrated analog I/O functions was FCC certification. The manufacturers developed a way of separating the analog circuitry, for example, modem and analog audio, onto its own card.
Identifying Components of Motherboards 17 same length as one of the portions of the AMR slot, but the other portion of the CNR slot is longer than that of the AMR slot. Essentially, these 60-pin slots allow a motherboard manufacturer to implement a motherboard chipset with certain integrated features.
18 Chapter 1 N Personal Computer System Components F I G U R E 1 .1 0 A CNR slot F I G U R E 1 .11 Different memory module form factors 30-pin SIMM (3.5 .75˝ ) 72-pin SIMM (4.25 1˝ ) 168-pin DIMM (5.375 1˝ ) 144-pin SODIMM (2.625 1˝ ) 72-pin SODIMM (2.375 1˝ ) Memory slots are easy to identify on a motherboard. DIMM slots are usually black and placed very close together. DIMM slots with pair-by-pair color coding can be observed these days, however.
Identifying Components of Motherboards 19 Sometimes the amount of primary memory installed is inadequate to service additional requests for memory resources from newly launched applications. When this condition occurs, the user receives an “out of memory” error, and the application fails to launch. One solution for this is to use the hard drive as additional RAM. This space on the hard drive is known as a swap file or a paging file. The technology in general is known as virtual memory.
20 Chapter 1 N Personal Computer System Components attached to it (as shown in Figure 1.12). These devices are used to draw away and disperse the heat a processor generates. This is done because heat is the enemy of microelectronics. Theoretically, a Pentium (or higher) processor generates enough heat that without the heat sink it would permanently damage itself and the motherboard in a matter of hours or even minutes. F I G U R E 1 .
Identifying Components of Motherboards 21 LGA-compatible sockets, as they’re called despite the misnomer, have a lid of sorts that closes over the CPU and is locked in place by an L-shaped arm that borders two of the socket’s edges. The nonlocking leg of the arm has a bend in the middle that latches the lid closed when the other leg of the arm is secured. The bottom image in Figure 1.13 shows an LGA socket with no CPU installed and the locking arm secured over the lid’s tab (righthand edge in the photo).
22 Chapter 1 N Personal Computer System Components The processor slot is another method of connecting a processor to a motherboard, but one into which a processor (such as the AMD Athlon or the Intel Pentium II or Pentium III) on a special expansion card is inserted (the slot shown in Figure 1.14). Newer, more complex processors, such as the Intel Itanium, use a similar packaging, known as a Pin Array Cartridge (PAC), which uses a complex mechanism for inserting the large rectangular PAC CPU carrier.
Identifying Components of Motherboards TA B L E 1 .1 86498book.
24 Chapter 1 TA B L E 1 .
Identifying Components of Motherboards F I G U R E 1 .1 5 25 An ATX power connector on a motherboard Today, the headers you will find on most motherboards are for Enhanced IDE (EIDE)— also known retroactively as Parallel ATA (PATA)—or Serial ATA (SATA). Advanced Technology Attachment (ATA) is the standard term for what is more commonly referred to as Integrated Drive Electronics (IDE). The AT component of the name was borrowed from the IBM PC/AT, which was the standard of the day.
26 Chapter 1 N Personal Computer System Components The 40-pin ATA header transfers data between the drive and motherboard multiple bits in parallel, hence the name Parallel ATA. SATA, in comparison, which came out later and prompted the retroactive PATA moniker, transfers data in serial, allowing a higher data throughput because there is no need for more advanced parallel synchronization of data signals. The SATA headers are vastly different from the PATA headers. Figure 1.
Identifying Components of Motherboards 27 about ½ inch in diameter, in a 5-pin DIN configuration. Figure 1.17 shows an example of the AT-style keyboard connector. The PS/2 connector (as shown in Figure 1.18) is a smaller 6-pin mini-DIN connector. Many new PCs you can purchase today contain a PS/2 keyboard connector as well as a PS/2 mouse connector right above it on the motherboard. Compare your PC’s keyboard connector with Figures 1.17 and 1.18. F I G U R E 1 .
Chapter 1 28 N Personal Computer System Components Newer motherboards have color-coded the PS/2 mouse and keyboard connectors to make connection of keyboards and mice easier. PS/2 mouse connectors are green (to match the standard green connectors on some mice), and the keyboard connectors are purple. Peripheral Ports and Connectors In order for a computer to be useful and have the most functionality, there must be a way to get the data into and out of it.
Identifying Components of Motherboards 29 as well. Game ports connect such peripheral devices to the computer using a DA-15F 15-pin female D-subminiature (D-sub) connector. Devices that once connected to the game port have evolved, for the most part, into USB-attached devices. F I G U R E 1. 2 0 A game port Figure 1.21 shows another set of interfaces not shown in Figure 1.19, the sound card jacks. These jacks are known as 1⁄8 -inch (3.
30 Chapter 1 N Personal Computer System Components Motherboard Attachment There are two ways of connecting these ports to the motherboard (assuming the circuitry for providing these functions is integrated into the motherboard). The first, called a header connection, allows you to mount the ports into the computer’s case, usually on the backplane, with a special cable connected to a header, or male connector that terminates the motherboard’s traces for that function, as shown in Figure 1.22.
Identifying Components of Motherboards 31 BIOS and POST Aside from the processor, the most important chip on the motherboard is the Basic Input/ Output System (BIOS) chip, also referred to as the ROM BIOS chip. This special memory chip contains the BIOS systems software that boots the system and allows the operating system to interact with certain hardware in the computer, in lieu of requiring a device driver to do so.
Chapter 1 32 N Personal Computer System Components The POST process can end with a beep code or displayed code that indicates the issue discovered. Each BIOS publisher has its own series of codes that can be generated. Figure 1.25 shows a simplified POST display during the initial boot sequence of a computer. F I G U R E 1. 2 5 An example of a BIOS boot screen CMOS and CMOS Battery Your PC has to keep certain settings when it’s turned off and its power cord is unplugged.
Identifying Components of Motherboards 33 from electrostatic discharge (ESD). Another ramification is that it doesn’t take much of a power source to keep CMOS chips from losing their contents. To prevent CMOS from losing its rather important information, motherboard manufacturers include a small battery called the CMOS battery to power the CMOS memory. The batteries come in different shapes and sizes, but they all perform the same function.
34 Chapter 1 N Personal Computer System Components Identifying Purposes and Characteristics of Processors Now that you’ve learned the basics of the motherboard, you need to learn about the most important component on the motherboard: the CPU. The role of the CPU, or central processing unit, is to control and direct all the activities of the computer using both external and internal buses. It is a processor chip consisting of an array of millions of transistors.
Identifying Purposes and Characteristics of Processors 35 motherboard. As a result, the grid of metallic contact points, called lands, on the bottom of the CPU gives this format its name. This discussion only scratches the surface of the topic surrounding chip packaging and carriers. For more information on the various packaging for chips, start with EN WIKIPEDIA ORG WIKI #ATEGORY #HIP?CARRIERS.
36 Chapter 1 N Personal Computer System Components Which CPU Do You Have? The surest way to determine which CPU your computer is using is to open the case and view the numbers stamped on the CPU, which today requires removal of the active heat sink. However, you may be able to get an idea without opening the case and removing the heat sink and fan, because many manufacturers indicate the type of processor by placing a very obvious sticker somewhere on the case indicating the processor type.
Identifying Purposes and Characteristics of Processors 37 processors come in Solo (mobile only), Duo, and four-core (Quad) implementations. Solo and Duo processors have a single die; Quad processors have two Duo dies. A more capable Extreme version exists for the Duo and Quad models. Processors, such as certain models of AMD’s Phenom series, can contain an odd number of multiple cores as well.
38 Chapter 1 N Personal Computer System Components Matching System Components In a world of clock doubling, tripling, quadrupling, and so forth, it becomes increasingly important to pay attention to what you are buying when you purchase CPUs, memory, and motherboards a la carte. The only well-known relationship that exists among these components is the speed of the FSB (in MHz) and the throughput of the memory (in MBps).
Identifying Purposes and Characteristics of Memory F I G U R E 1. 2 9 39 Location of memory within a system Memory Important Memory Terms There are a few technical terms and phrases that you need to understand, with regard to memory and its function. These include: Nß Parity checking Nß Error checking and correcting (ECC) Nß Single- and double-sided memory Nß Single- and dual-channel memory These terms are discussed in detail in the following sections.
40 Chapter 1 N Personal Computer System Components a memory bank. A bank of memory is required for the computer system to electrically recognize that memory or additional memory has been installed. The width of the system data bus, the external bus of the processor, dictates how many memory chips or modules are required to satisfy a bank. For example, one 32-bit, 72-pin SIMM satisfies a bank for a 32-bit CPU, such as a 386 or 486 processor.
Identifying Purposes and Characteristics of Memory 41 Single- and Double-Sided Memory Ask just about anyone who doesn’t manufacture memory for a living what the terms singlesided memory and double-sided memory mean, and you’ll be treated to a blank stare or a short diatribe on how some memory modules have chips on one side, while others have chips on both sides. In fact, these terms have nothing to do with the physical attachment of chips to the modules.
42 Chapter 1 N Personal Computer System Components Although it’s not the make-up of the memory that leads to dual-channel support, but instead the technology on which the motherboard is based, some memory manufacturers still package and sell pairs of memory modules in an effort to give you peace of mind when you’re buying memory for a system that implements dual-channel memory architecture. Keep in mind, the motherboard memory slots have the distinctive color coding, not the memory modules.
Identifying Purposes and Characteristics of Memory 43 or marketability to computer manufacturers. The following list gives you an idea of the vast array of memory types and subtypes: Nß DRAM Nß Nß Asynchronous DRAM Nß FPM DRAM Nß EDO DRAM Nß BEDO DRAM Synchronous DRAM Nß SDR SDRAM Nß DDR SDRAM Nß DDR2 SDRAM Nß DDR3 SDRAM Nß DRDRAM Nß SRAM Nß ROM Pay particular attention to all synchronous DRAM types. Note that the type of memory does not dictate the packaging of the memory.
44 Chapter 1 N Personal Computer System Components time is essentially the difference between the time when the information is requested from memory and the time when the data is returned. Common access times attributed to asynchronous DRAM were in the 40- to 120-nanosecond (ns) vicinity. A lower access time is obviously better for overall performance.
Identifying Purposes and Characteristics of Memory 45 falling edges of the clock signal. This obtains twice the transfer rate at the same FSB clock frequency. It’s the increasing clock frequency that generates heating issues with newer components, so keeping the clock the same is an advantage. The same 100MHz clock gives a DDR SDRAM system the impression of a 200MHz clock in comparison to an SDR SDRAM system. For marketing purposes and to aid in the comparison of disparate products (DDR vs.
46 Chapter 1 N Personal Computer System Components Let’s try another. What do you need for a motherboard that features a 333MHz FSB (actual clock is 166MHz)? Well, just using the 8:1 rule mentioned earlier, you might be on the lookout for a PC2667 module. However, note that sometimes the numbers have to be played with a bit to come up with the industry’s marketing terms. You’ll have an easier time finding PC2700 modules that are designed specifically for a motherboard like yours, with an FSB of 333MHz.
Identifying Purposes and Characteristics of Memory 47 The most commonly found range of actual clock speeds for DDR3 tends to be from 133MHz at the low end to 250MHz. Because double-pumping continues with DDR3 and because four operations occur at each wave crest (8 operations per cycle), this frequency range translates to common FSB implementations from 1066MHz to 2000MHz in DDR3 systems. Naming these memory devices follows the conventions established earlier.
48 Chapter 1 N Personal Computer System Components special licensing considerations and royalties from Rambus. The contract ran from 1996 until 2002. In 1999, Intel launched the first motherboards with DRDRAM support. Until then, Rambus could be found mainly in gaming consoles and home theater components. DRDRAM did not impact the market as Intel had hoped, and so motherboard manufacturers got around Intel’s obligation by using chipsets from VIA Technologies, leading to the rise of that company.
Identifying Purposes and Characteristics of Memory TA B L E 1 . 2 49 How Some Memory Types Transfer 3200MBps per Channel Memory Type Actual/Effective (FSB) Clock Frequency (MHz) Bytes per Transfer SDR SDRAM PC400* 400/400 8 DDR SDRAM PC3200 200/400 8 DDR2 SDRAM PC2-3200 100/400 8 DDR3 SDRAM PC3-3200** 50/400 8 DRDRAM PC800 400/800 4*** * SDR SDRAM PC400 does not exist. **PC3-3200 does not exist and is too slow for DDR3.
Chapter 1 50 N Personal Computer System Components but then no more. You had a new bug to keep the ROM bug company. Liken this to the burning of a CD-R. Don’t need it any longer? You’ve got a handy coaster. Following the PROM came erasable PROM (EPROM), which was able to be erased using ultraviolet light and subsequently reprogrammed using the original programming device.
Identifying Purposes and Characteristics of Memory 51 With 84 pins per side, this makes 168 independent pins on each standard SDR module, as shown with its two keying notches as well as the last pin labeled 84 on the side shown in Figure 1.30. F I G U R E 1.
52 86498book.indb 52 Chapter 1 N Personal Computer System Components F I G U R E 1. 3 2 A pair of DDR3 SDRAM modules F I G U R E 1.
Identifying Purposes and Characteristics of Memory 53 As mentioned earlier, DRDRAM is based on a 16-bit channel. However, dual-channel implementation is required with DRDRAM; it’s not an option. The dual-channel architecture can be implemented utilizing two separate 16-bit RIMMs (leading to the generally held view that RIMMs must always be installed in pairs) or the newer 32-bit single-module design (not doing much to dispel the “pair” view, despite the facts).
54 Chapter 1 N Personal Computer System Components F I G U R E 1. 3 4 144-pin SODIMM F I G U R E 1. 3 5 200-pin DDR2 SODIMM Identifying Characteristics of Ports and Cables Now that you’ve learned the various types of items found in a computer, let’s discuss the various types of ports and cables used with computers. A port is a generic name for any connector on a computer into which a cable can be plugged.
Identifying Characteristics of Ports and Cables 55 Peripheral Port Connector Types Computer ports are interfaces that allow other devices to be connected to a computer. Their appearance varies widely, depending on their function.
56 Chapter 1 F I G U R E 1. 3 6 N Personal Computer System Components D-sub ports and connectors RJ-Series Registered jack (RJ) connectors are most often used in telecommunications. The two most common examples of RJ ports are RJ-11 and RJ-45. RJ-11 connectors are used most often in telephone hookups; your home phone jack is probably an RJ-11 jack. The ports in your external and internal modems, assuming you still have one, are RJ-11.
Identifying Characteristics of Ports and Cables Nß Audio jacks Nß PS/2 (mini-DIN) Nß Centronics 57 Let’s look at each one and how it is used. F I G U R E 1. 3 7 RJ ports Universal Serial Bus (USB) Most computers built after 1997 have one or more flat ports in place of one DE9M serial port. These ports are Universal Serial Bus (USB) ports, and they are used for connecting multiple (up to 127) peripherals to one computer through a single port (and the use of multiport peripheral hubs). USB version 1.
58 Chapter 1 F I G U R E 1. 3 8 N Personal Computer System Components USB ports Because of USB’s higher transfer rate, flexibility, and ease of use, most devices that in the past used serial interfaces now come with USB interfaces. It’s rare to see a newly introduced PC accessory with a standard serial interface cable. For example, PC cameras used to come as standard serial-only interfaces. Now you can buy them only with USB interfaces.
Identifying Characteristics of Ports and Cables 59 Infrared Increasing numbers of people are getting fed up with being tethered to their computers by cords. As a result, many computers (especially portable computing devices like laptops and PDAs) are now using infrared ports to send and receive data. An infrared (IR) port is a small port on the computer that allows data to be sent and received using electromagnetic radiation in the infrared band.
60 Chapter 1 F I G U R E 1 . 41 N Personal Computer System Components An RCA jack (female) and RCA plug (male) Female Male Today, RCA jacks and connectors (or plugs) are used to transmit both audio and video information. Typically, when you see a yellow-coded RCA connector on a PC video card (next to a DE15F connector), it’s for composite video output (output to a television or VCR). However, digital audio can be implemented with S/PDIF, which can be deployed with an RCA jack. Figure 1.
Identifying Characteristics of Ports and Cables 61 PS/2 (Keyboard and Mouse) Another common port, as mentioned earlier, is the PS/2 port. A PS/2 port (also known as a mini-DIN 6 connector) is a mouse and keyboard interface port first found on the IBM PS/2 (hence the name). It is smaller than previous interfaces (the DIN-5 keyboard port and serial mouse connector), and thus its popularity increased quickly. Figure 1.43 shows examples of both PS/2 keyboard and mouse ports.
Chapter 1 62 N Personal Computer System Components Centronics The last type of port connector is the Centronics connector, a micro ribbon connector named for the Wang subsidiary that created it. It has a unique shape, as shown in Figure 1.44. It consists of a central connection bar surrounding by an outer shielding ring. The Centronics connector was primarily used in parallel printer connections and SCSI interfaces.
Identifying Characteristics of Ports and Cables 63 Parallel For many years, the most popular type of interface available on computers was the parallel interface. Parallel communications take the interstate approach to data communications. Normally, interstate travel is faster than driving on city roads. This is the case mainly because you can fit multiple cars going the same direction on the same highway by using multiple lanes.
64 Chapter 1 N Personal Computer System Components with the standard and bidirectional ports and support cable lengths of 4.5 meters, which is almost 15 feet. There are two implementations of IEEE 1284: EPP parallel ports and ECP parallel ports. An enhanced parallel port (EPP) increases bidirectional throughput from 150KBps to anywhere from 600KBps to 1.5MBps. An enhanced capabilities port (ECP) is designed to transfer data at even higher speeds, around 2MBps.
Identifying Characteristics of Ports and Cables F I G U R E 1. 4 6 65 The mini-Centronics connector Serial If standard parallel communications were similar to taking the interstate, then RS-232 serial communications were similar to taking a country road. In serial communications, bits of data are sent one after another (single file, if you will) down one wire, and they return on a different wire in the same cable.
66 Chapter 1 N Personal Computer System Components F I G U R E 1. 47 Standard DE-9 and DB-25 male serial ports F I G U R E 1. 4 8 A standard serial cable wiring diagram 1 13 14 25 DB-25 Male F I G U R E 1.
Identifying Characteristics of Ports and Cables TA B L E 1 .
68 Chapter 1 N Personal Computer System Components Be aware of the limitations in the USB specification. The commonly quoted length limit for USB cables is 5 meters. If you use hubs, you should not use more than 5 hubs between any two components. Through the use of a 7-bit identifier, overall, no more than 127 devices, including hubs, should be connected back to a single USB host controller in the computer, not that you would ever want to approach this number. The 128th identifier is used for broadcasting.
Identifying Characteristics of Ports and Cables 69 Type B plugs connect in the direction of the component. Therefore, you see a Type B interface on the hub as well as on the end devices to allow them to cable back to the system or another hub. Although they exist, USB cables with both ends of the same type, a sort of extension cable, are in violation of the USB specification. Collectively, these rules make cabling your USB subsystem quite straightforward.
70 Chapter 1 F I G U R E 1. 5 2 N Personal Computer System Components A FireWire (IEEE 1394) alpha cable Because the FireWire specification was conceived to allow peripherals to be networked together in much the same fashion as intelligent hosts are networked together in LANs and WANs, a quick introduction to the concept of networking is in order; see Chapter 10 for more detail on networking concepts.
Identifying Characteristics of Ports and Cables F I G U R E 1. 5 3 71 An RCA cable The RCA male connectors on a connection cable are sometimes plated in gold to increase their corrosion resistance and to improve longevity. PS/2 (Keyboard and Mouse) The final interface we’ll discuss is the PS/2 interface for mice and keyboards. Essentially, it is the same connector for the cables from both items: a male mini-DIN 6 connector.
72 Chapter 1 N Personal Computer System Components Identifying Purposes and Characteristics of Cooling Systems It’s a basic concept of physics: electronic components turn electricity into work and heat. The heat must be dissipated or the excess heat will shorten the life of the components. In some cases (like the CPU), the component will produce so much heat that it can destroy itself in a matter of seconds if there is not some way to remove this extra heat.
Identifying Purposes and Characteristics of Cooling Systems 73 Memory module fan The more capable our memory becomes of keeping up with our CPU, the hotter it runs. As an extra measure of safety, regardless of the presence of heat spreaders on the modules, an optional fan setup for your memory might be in order. See the following section for more. Ideally, the airflow inside a computer should resemble what is shown in Figure 1.55. F I G U R E 1.
74 Chapter 1 N Personal Computer System Components enhanced heat dissipation. For this, you can buy either heat sinks or, as mentioned earlier, special “for memory chips only” devices known as heat spreaders. These are special aluminum or copper housings that wrap around memory chips and conduct the heat away from the memory chips. Active cooling, on the other hand, usually involves forcing some kind of cooling medium (air or water) around the RAM chips themselves or around their heat sinks.
Identifying Purposes and Characteristics of Cooling Systems 75 Air Cooling The parts inside most computers are cooled by air moving through the case. The CPU is no exception. However, because of the large amount of heat produced, the CPU must have (proportionately) the largest surface area exposed to the moving air in the case. Therefore, the heat sinks on the CPU are the largest of any inside the computer.
76 Chapter 1 N Personal Computer System Components Improving and Maintaining CPU Cooling In addition to using thermal compound, you can enhance the cooling efficiency of a CPU heat sink by lapping the heat sink, which smoothes the mating surface using a very fine sanding element, about 1000-grit in the finishing stage. Some vendors of the more expensive heat sinks will offer this service as an add-on.
Identifying Purposes and Characteristics of Cooling Systems 77 Liquid Cooling Liquid cooling is a technology whereby a special water block is used to conduct heat away from the processor (as well as from the chipset). Water is circulated through this block to a radiator, where it is cooled. The theory is that you could achieve better cooling performance through the use of liquid cooling. For the most part, this is true.
78 Chapter 1 N Personal Computer System Components One of the downsides to TECs is the likelihood of condensation because of the subambient temperatures these devices produce. Closed-cell foams can be used to guard against damage from condensation. Phase-Change Cooling There is one new type of PC cooling that is just starting to be seen: phase-change cooling. With this type of cooling, the cooling effect from the change of a liquid to a gas is used to cool the inside of a PC.
Exam Essentials 79 Exam Essentials Know the types of system boards. Know the characteristics of and differences between ATX, micro ATX, NLX, and BTX motherboards. Know the components of a motherboard.
Chapter 1 80 N Personal Computer System Components Review Questions 1. Which computer component contains all the circuitry necessary for other components or devices to communicate with one another? A. Motherboard 2. B. Adapter card C. Hard drive D. Expansion bus Which packaging is used for DDR SDRAM memory? A. 168-pin DIMM B. 3. 72-pin SIMM C. 184-pin DIMM D. RIMM What memory chips would you find on a stick of PC3-16000? A. DDR-2000 4. B. DDR3-2000 C. DDR3-16000 D.
Review Questions 7. 81 Which of the following is not controlled by the Northbridge? A. PCIe B. 8. SATA C. AGP D. Cache memory Which of the following is used to store data and programs for repeated use? Information can be added and deleted at will, and it does not lose its data when power is removed. A. Hard drive B. 9. RAM C. Internal cache memory D. ROM Which motherboard socket type is used with the AMD Athlon XP? A. Slot 1 B. Socket A C. Socket 370 D. Socket 478 10.
Chapter 1 82 N Personal Computer System Components 13. Which of the following standards are specified by IEEE 1284? (Choose two.) A. SPP B. RS-232 C. EPP D. ECP E. FireWire F. USB 14. What peripheral port type was originally developed by Apple and is currently the optimal interface for digital video transfers? A. DVD B. USB C. IEEE 1394 D. IEEE 1284 15. What peripheral port type is expandable using a hub, operates at 1.
Review Questions 83 19. You have just purchased a motherboard that has an LGA775 socket for an Intel Pentium 4 processor. What type of memory modules will you need for this motherboard? A. DIP B. SIMM C. RIMM D. DIMM 20. What type of expansion slot is preferred today for high-performance graphics adapters? A. AGP B. 86498book.indb 83 PCIe C. PCI D.
84 Chapter 1 N Personal Computer System Components Answers to Review Questions 1. A. The spine of the computer is the system board, otherwise known as the motherboard. On the motherboard you will find the CPU, underlying circuitry, expansion slots, video components, RAM slots, and various other chips. 2. C. DDR SDRAM is manufactured on a 184-pin DIMM. DIMMs with 168 pins were used for SDR SDRAM. The SIMM is the predecessor to the DIMM, on which SDRAM was never deployed.
Answers to Review Questions 85 11. A, C, G. DIMMs used in desktop-motherboard applications have one of three possible pin counts. SDR SDRAM is implemented on 168-pin modules. DDR SDRAM and 16-bit RIMMs are implemented on 184-pin modules. DDR2 and DDR3 are implemented on 240-pin modules with different keying. Dual-channel RIMM modules have 232 pins. Modules with 200 and 204 pins are used in the SODIMM line, and there are no modules with 180 pins. 12. D. The USB 2.