PC Hardware

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 h1. Introduction to PC Hardware
  
 The newspaper ads scream out prices, MHz, SATA,&nbsp;DDR3, PCI-e. Do you know what these buzzwords really mean? Does anyone? The PC may be the single most important tool for researchers and executives, but because it is purchased in an office supply store or discount food warehouse it is often treated as a commodity item.
  
 It would be hard to find a vendor with substandard parts. You might buy a washing machine that breaks down just after the warranty runs out, but a computer has few moving parts (some fans and the disk) so there is nothing to wear out. If they built a bad machine, it is just as likely to fail out of the box as two years later. In 2007 some mainboard vendors received shipments of counterfeit capacitors, poor quality parts marked as more expensive components. This is one of the few parts that can overheat, swell and break over time. After those failures the industry added new checks to prevent such things happening in the future, and mainboards today often advertise "all solid state capacitors" while a few years ago nobody would have thought to even ask.
  
 This is not to say that system builders don't cut corners. It's just that the corners don't involve substandard components. Instead, they leave out inexpensive upgrades that consumers aren't smart enough to look for. For an extra $20 they can offer a 320G hard drive instead of an 80G disk. For a few dollars they could use less noisy fans. You can get a cheap case (with sharp edges that cut your hands), but if you never open the covers you will never know. So in an era where game consoles cost $600, and you can spend real money on a flat panel TV set, you can still buy the least expensive Dell or HP system for $350 and get a pretty good computer. If that is all the advice you are looking for, read no farther.
  
 The expert or enthusiast will read articles in [Tom's Hardware|http://www.tomshardware.com/]&nbsp;or [The Tech Report|http://techreport.com/]. The problem with these sites is that even their introductory articles assume some technical background and they really don't explain how things work. That is the purpose of this page and its linked to articles. The background information may have no immediate practical use, but it will increase your comfort level. If the PC is no longer a big investment in money, it is still an important tool in business or education. Knowing more about it should make concerned people more comfortable with their decisions. No technical background is assumed. Even very complex issues will be explained in terms that everyone can understand.
  
 h2. The Most Common Problems are Simple
  
 *Backup your files -* Every week someone loses their family pictures or their Senior thesis. Every disk will eventually stop working. Some will stop sooner than others. Buy an external hard drive or USB flash stick and make a copy of everything you spend more than 10 minutes creating or editing. As you become more professional (or get burned a few times) you will begin to make two backup copies using either very simply file copy or two entirely different backup programs. Some backups make it easy to recover an entire failed disk, while other backups are better at recovering a single file that you accidentally damaged.
  
 Do not assume that a backup program works unless you have restored something. Lots of people simply check that the backup appeared to work and assume they are safe. Restore the files to another disk or at least a different part of the disk and check to make sure they are all correct.
  
 *Malware* \- Today a lot more computers get discarded because virus programs and other malware have made them unusable than because some hardware has failed. Since most users don't know how to reformat the disk and reinstall Windows from scratch, they buy a new computer. Don't fall into this trap. Buy real software at the store or from reputable online sources. Follow the instructions to turn on automatic updating by Microsoft. After that: *Just say No\!* When something pops up on your screen and tells you that your system is full of disease and offers to install something to fix it, *Just* *say No*. When an add promises to clean your registry, or disk, or make network downloads faster, *Just say No*. When you are offered free porn from Eastern Europe, *Just say* *No*.
  
 *Vacuum Regularly* \- The enemy of a computer is heat. Computers have fans to move air around disks and metal heat sinks to cool the components, but the fans and cooling fins can become clogged with dust, dog hair, and any other gunk floating in the air. If you never open the computer, you don't see the problem. To avoid problems, turn the machine off, unplug it, open the cover, and vacuum the screens, fans, and fins. Don't forget the power supply. If there is a filter, clean it.
  
 h2. Who Made It?
  
 IBM invented the modern PC design, but they recently sold that business to a Chinese company. This should not be a big surprise. Often the only American thing in a computer is the name on the cardboard box it came in. Apple assembles systems in Shanghai and ships them overnight to the US.
  
 If you buy a car from Ford, you expect the frame, engine, transmission, generator, and other parts to come from Ford or at least be built to Ford specifications. You do not expect to be able to put a Ford transmission in a GM car.
  
 In a PC, however, the CPU, memory, disk,&nbsp;CD, power supply, and case are all manufactured to industry standards. You can take a hard disk or memory out of a Dell computer and put it into a system made by HP. The brand names you know are the names of companies that assemble, distribute, and support the computers, not the companies that make the parts.
  
 This is an international business. The mainboard almost certainly comes from a Taiwan company (Asus, Abit, Shuttle, MSI, ...). Disks tend to come from Singapore or Indonesia (Seagate, Western Digital, Maxtor). Memory and LCD displays often come from Korea. The external case and the power supply probably come from China (though over time more and more parts will come from China).
  
 You can buy the components from [CDW|http://www.cdw.com] or [NewEgg|http://www.newegg.com] and assemble a computer yourself, but you won't save any money. The big computer makers buy parts in lots of a thousand, packaged in bulk to save packing and shipping. Nine screws attach the motherboard to the mounts on the case. Four screws attach the disk to the disk bay. Then the cables all plug into sockets. An unskilled worker can be quickly trained to assemble a computer every few minutes. You can learn to do it from scratch in a few hours, so if you are looking for an electronics project to keep you busy for weeks, go build a shortwave radio.
  
 The advanced technology is in the manufacture of the chips, not the final assembly of the finished product. A CPU chip is constructed in a plant that costs billions of dollars. The building is on shock absorbers because the vibration generated by passing trucks would disturb the process. People wear spacesuits not to protect them from the environment, but to protect the chips from flakes of loose skin or the particles we exhale in every breath.
  
 Then the chip is packaged in plastic and shipped out. There is a socket on the mainboard. One corner of the chip has an arrow, and one corner of the socket has an arrow. Drop the chip into the socket while matching the two arrows, then drop a lever to hold it in place.&nbsp; It is harder to tie a shoelace than to install a CPU chip on a mainboard.
  
 h2. Technical Trends
  
 There are trends that have developed over the last three years, and strategies that may say something about what computers will look like three years from now. Knowing this stuff makes you informed, but it won't help you to decide what to buy today. These subjects are optional, so you can follow the links to the related articles if you are interested.
  
 [Intel and AMD|PCLT:IntelandAMD]
  
 [Duo and Quad|DuoQuad]
  
 [The GPU and Specialized Processors|GPU]
  
 [Overclocking|Overclock]
  
 h2. Standards
  
 There are 8 basic parts to a computer:
 # [Case|Case Choices]
 # [Power Supply|Power Supply Choices]
 # [Mainboard|Mainboard Choices]
 # [CPU|CPU Choices] (and cooling tower)
 # [Memory|Memory Choices]
 # [Video|Video Choices]
 # [Hard Disk|Hard Disk Choices]
 # [DVD Drive|DVD Choices]
  
 h3. All you need is a Phillips Screwdriver
  
 _\[For another description with pictures (but oriented to more powerful high-end systems), read this_ [_step by step guide from The Tech Report_|http://techreport.com/articles.x/13671]\_.\]\_
  
 &nbsp;You can buy every part (except the CPU) from a dozen different vendors. There are only two CPU choices. Everything will fit together because there are standards. Lets build the system.
 # The Power Supply is a metal box with cables that dangle from it and connect to devices inside the case. You slide it into place and attach it to the back of the case with four Phillips screws (that come with the Power Supply).
 # The mainboard sits on screw holes on top of nine "standoffs" that keep the bottom of the board a quarter inch away from the metal of the case tray. Standoffs and the screws that attach the mainboard come with the case. In almost every case these are the same size screws as the ones that hold the Power Supply.
 # A modern power supply has a 24 pin connector that plugs into a slot on the mainboard. There is a second 4 pin connector. There is a latch on one side of each plug that attaches to a plastic notch on one side of the mainboard socket, but the plugs have shapes so they cannot be plugged in upside down.
 # The CPU drops into the socket and clamps in place. A cooling tower (heat sink and fan) clamps on top of the mounting assembly on the mainboard. Plug the fan into the little 3 pin power connector on the mainboard.
 # Plug memory into the memory slots. If they don't go in at first, you may be trying to plug them in backwards.
 # Plug the video card in the long PCI Express slot.
 # The hard disk and DVD drive connect to the case with four screws, typically two screws on each side. These screws also come with the case, but they are slightly smaller than the screws that hold the mainboard to the standoffs. There are only the two sizes of screws.
 # Now plug the long thin SATA cable to SATA socket number 1 on the mainboard and connect it to the back of the disk. There is an L shaped connector so it cannot go in wrong. Connect a power cable from the power supply to the back of the disk.
 # Now there is a block of pins on the mainboard and some little cables from the front panel of the machine. Typically you connect the power switch, power light, disk light, and speaker cables. There will be a diagram in the manual for the mainboard. The power and disk light connectors are the only things in the computer that you can plug in backwards. If either light does not go on, open the case later and flip the connector around.
 # Connect the monitor, keyboard, and mouse. Plug the power cable in the wall and turn the machine on. It is time to install an operating system.
  
 The first time you do all this you may spend hours checking and rechecking everything. When you get used to it, the whole process can take as little as 20 minutes. On an assembly line, a worker probably builds a system in 3 minutes.
  
 h2. Carburetor or Cup Holders?
  
 Back in the 1950's, before fuel economy and pollution controls, people judged a car by the power of its engine. Today, however, cars are sold to the mass market based on a quiet smooth ride, side air bags, a nice sound system, and Cup Holders.
  
 There is a "hot rod" market for custom computers today. As with the automotive hot rod, the target audience for high performance computers are young males playing games. They have even borrowed a word from automotive customization, buying "modding" hardware for their systems. Cases have transparent panels and low heat internal lights to show off the electronics. The CPU is "overclocked" (run at a speed higher than that recommended by the manufacturer) and the extra heat is removed with exotic cooling systems. As with cars, this is a specialty market.
  
 Maybe it's the lower speed limits, or maybe the boomers are just getting older. Big engines are less important than they used to be. Some people even dream of zipping through town on a Segway. The same thing may happen with computers. The 55 to 65 miles per hour boundary for computers may correspond to 700 MHz to 1 GHz. That is fast enough to run Windows, browse the Web, read E-Mail, listen to MP3 files, and run all the Office programs. Faster speeds are only useful if you play computer games, convert video files, or run a server.
  
 This is not a message that the computer makers want you to hear. It might suggest to people that they keep their old computer for another year rather than replacing it with a new model. However, technology continues to evolve across the board, and CPU may not be the most important thing. You didn't buy your last new car because the speed limit increased on the highway.&nbsp; Consider some other issues:
  * *Green.* There is a significant addtional power cost when you upgrade to the highest available clock speed, or from a dual core to a quad core CPU. If you add one or two of the most powerful video adapters for gaming, each will use more power than the rest of the system combined. So desktop computers sold to enthusiasts have power supplied rated to handle 700 to 1000 watts. Alternately, for $350 you can buy an Asus Eee desktop unit that is the size of a paperback book. It has an Intel Atom low power processor and runs drawing between 17 and 21 watts of power for the whole system (including some USB devices, but excluding the monitor). It has a DVI connector and can run one large flat panel screen quite nicely. It comes with Windows XP and&nbsp;will surf the web, handle EMail, and run Office (not included, although Star Office is preinstalled).&nbsp;This is just the start of a new trend. Intel is about to release a dual core Atom processor, next&nbsp;year they will have a new better chipset (hopefully with better video), and Asus would&nbsp;do well to offer a choice of disk sizes&nbsp;beyond the current 80G. However, with enegy costs what they are and considering global warming, this is a very&nbsp;attractive package.
  * *Green.* A simple desktop computer draws around 100 watts of power. A system designed for gaming&nbsp;overclocks the most powerful quad processor and adds several of the most powerful video cards,&nbsp;requring a power supply rated for 1000 watts. It is the Hummer of computers.&nbsp;A laptop uses much less energy, but it costs more if you don't need the portability.&nbsp;The $350 Asus Eee PC, which&nbsp;uses laptop parts&nbsp;to create a tiny desktop&nbsp;computer.&nbsp;The system is about the size of a paperback book. It has an Intel Atom processor, laptop-style 2.5" disk, full size keyboard and mouse, and a DVI connector for one external flat panel monitor. It idles at 17 watts and runs real work at 21 watts. Think of it as a 1.6 GHz first generation&nbsp;Pentium CPU. It runs windows and Office quite nicely and can share files with other machines. If the current model is not quite powerful enough, Intel has announced a dual core Atom&nbsp;chip (though what they really need is a better chip set with modern graphics).
 * *Noise*. Look for a power supply and case with 120 mm fans that run at low speed. They provide adequate cooling with low noise. Alternately a low power system like the Eee desktop generates no noise at all.
 * *Keyboard and Mouse*. The keyboard is the one part of the computer system that arguably has gotten worse over the years instead of better. When IBM first designed its personal computer, they used the same keyboard technology used in other IBM devices designed for full time professional use. Some people believe that the old "clicky key" IBM keyboards of the 1980's represented the peak of technology. Today a "keyboard" is a no-cost item you can select on the Dell Web page, and replacement keyboards are sold in computer stores for $15. Compare this cost to the medical expenses of a repetitive stress injury. Fortunately, keyboards are interchangeable across systems, and a good one never breaks (although it doesn't improve if you spill pancake syrup into it). If you get a computer with a lousy keyboard, invest in a better one. Similarly, you can spend a few extra dollars getting a comfortable mouse and save your hand (although it is a lot easier to find mice shaped for right handed than left handed people).
 * *Screens*. Size matters. Anybody reading this document wants some kind of LCD monitor. They come in two flavors. Devices sold as computer monitors have a limited brightness and tend to have high resolution on small screen sizes. Today the 19" monitor has become standard, but there are 20" and 24" monitors, some with wide screens. For a bit more you can buy an LCD TV. When sold as a TV, the screen is typically twice as bright as a computer monitor. TV panels (32" to 42") have resolutions of approximately 1280x768 or 1920x1080. A smaller 24" screen sold as a computer monitor will have resolutions of 1600x1200. Baby Boomers will discover that higher resolution isn't necessarily a good thing. While it makes photographs sharper, it also makes text too small to read comfortably.
  
 High performance computers run games that appeal to the teenager. For the rest of us, a comfortable keyboard, easy to read screen, and quiet room may be more important.
  
 h2. The Q Bridge
  
 In downtown New Haven, CT where I-91 meets I-95, the "Q Bridge" crosses the harbor area. It must be one of the hottest attractions in southern New England, because every morning and afternoon cars line up for miles to cross it. It defines the rush hour commute, and nothing that you do to the other roads or exits in West Haven or East Haven will materially speed things up.
  
 Inside your computer there is an electronic version of the Q Bridge. Depending on the application, some component will become the choke point, and all the data bytes will line up waiting to get through. But while the real Q Bridge never changes, the PC choke point moves as you change use.
  
 A Porche and a Yugo get caught in the backup at the same point in West Haven. Twenty minutes later they cross the bridge at the same time. It doesn't do any good to spend a lot of money on a fast car and a big engine if the limiting factor is traffic moving five miles an hour. Yet customers often select a server with a fast CPU, without first considering what the bottleneck will be.
  
 If you play video games or edit video, then the speed of your computer depends on the speed of the CPU. If you record TV shows on your computer and then edit out undesirable material periodically inserted into the program, processing may be 10 times faster if you read from one disk and write to another than if you use a single disk. The performance of a database is typically determined by the amount of memory you have. Copying files from one machine to another depends on the network speed.
  
 h2. Summary and Links to Topics
  
 Each main point will be summarized here. The summary is then linked to a secondary page where you can learn more about a particular topic. Readers are urged to follow each such link to get the full story, but you can make your own decision.
  
 h3. Circuit Size, Voltage, and Heat
  
 All the electronic components of a computer follow some basic design principles. To make a computer circuit operate faster, you have to make it smaller. Smaller circuits can run at a higher speed, using less voltage, and producing less heat. By analogy, if the only question is 0 or 1, empty or full, then it is much faster and requires much less work to fill a shotglass with water than to fill a bathtub. These four factors (size, speed, voltage, and heat) are always in balance. You can increase speed on a given chip by increasing the voltage, but that produces more heat and requires more expensive cooling. [For more information ...|size]
  
 h3. Clocks and Cycles
  
 Components of a computer (the CPU, memory, adapter cards) are coordinated by a "clock" signal measured in Megahertz (millions of ticks per second) or Gigahertz (billions of ticks per second). Generally we say that speeding up the clock makes the computer run faster, but that is slightly misleading. The clock tells all the components when they should all be done with their previous operation and when they should begin the next step. Components all run at whatever speed their design permits. If all the components can complete their longest operation with lots of time to spare, then there is room to speed up the clock, shorten the periods, and get more work done in the same amount of time. Set the clock too fast ("overclock") and it ticks before one of the components is quite done with its last operation. Then the system crashes.&nbsp; [For more information ...|clock]
  
 h3. CPU, Instructions
  
 A computer chip can do simple arithmetic, compare numbers, and move numbers around in memory. Everything else, from word processing to browsing the Web, is done by programs that use those basic instructions. CPUs get faster in three ways. First, better designs can do the simple operations faster. Second, better design can do as many as six simple operations at the same time in different areas of the CPU. Thirdly, since a lot of time is lost if the CPU has to wait for data from slower memory, techniques that reduce the memory wait time appear to speed up the CPU. [For more information ...|cpudesign]
  
 h3. Hyperthreading and Multi-Core
  
 The processing steps of a computer program can be decomposed into a set of independent "threads". To display a Web page, the Browser has to read in the page itself plus each individual file representing the pictures and ads displayed within the page. Then the text has to be arranged on the page and each picture has to be decompressed. Finally, the page has to be arranged and displayed on the screen. Each of these operations can be assigned to a thread. If a computer has (or appears to have) two CPUs, Windows will assign a separate thread to each processor and the computer will process two different streams of data at the same time.
  
 No matter how fast Intel makes its chip, a modern CPU spends 50% or more of its time waiting for data to arrive from main memory. This is only getting worse, because CPU speed increases much more quickly than memory speed. A larger cache provides some help. Another idea, however, is for the CPU to have some way to switch from the instruction and thread that is blocked waiting for data to another thread that is ready to execute. This is the idea behind "Hyperthreading". Each CPU pretends to be two processors. The OS assigns a thread to each pretend processor. When one thread is blocked waiting for data, the CPU can switch over to the other thread and get more work done. [For more information ...|hyperthreading]
  
 h3. Memory and "Burst" Speed
  
 Technology has been applied to increase memory speed only when it can be done without reducing size or increasing cost. Current mass market designs favor Double Data Rate SDRAM. When a CPU instruction requires data from memory, it presents the address and then has to wait several cycles. Once the first block of data has been located by the memory hardware, the 32 bytes immediately surrounding the address can also be transferred in a "burst" of activity. DDR memory transfers the data at twice the ordinary speed of the memory bus by transferring bytes on both the tick and the tock of the clock. [For more information ...|memories]
  
 h3. The Mainboard (Motherboard)
  
 The mainboard contains slots for the CPU, memory, and I/O devices. In current designs, one chip called the Northbridge&nbsp; sits between and connects the three high speed devices: CPU, memory, and AGP video port. It is then connected to a second chip called the Southbridge that provides logic for all the slow speed devices: the keyboard, mouse, modem port, printer port, IDE controller, PCI, USB, and any other devices. [For more information ...|mainboard]
  
 h3. Hard Disks and CD Drives
  
 Apple adopted an industry standard technology called SCSI for its Macintosh computers. It was a standard that applied to desktops, servers, and even mainframe computers. PC makers, however, followed a path of tricks and gimmicks to design the lowest cost disk attachment. The simplest possible electronic interface was a chip that duplicated exactly the mainboard I/O bus available at the time. A simple 40 wire cable connected this chip to logic chips on the disk. The mainboard bus had been introduced on the IBM PC AT in 1985, so the disk connection became knows as AT Attachment or "ATA". It is also popularly known as "IDE" but some manufacturer claimed that as a trademark barring its use as an official name. Then a dozen years passed, and each year the chips got twice as smart as the year before. ATA evolved from an 8 MHz connection to a 133 MHz connection and became smart enough to handle other types of devices. However, the physical connectors and programming interface had to build on and remain compatible with an idea that some engineers developed to build the lowest cost possible interface based on the primitive electronics available at that moment in time. Today computers are transitioning to a new simpler and higher speed interface called Serial ATA. [For more information ...|idescsi]
  
 h3. Video and Monitors
  
 The video adapter requires higher data transfer speeds than any other device. While the disks and network plug into the PCI bus or Southbridge mainboard chip, the video adapter is connected at high speed to the CPU and memory. For a decade, the video connector has been an AGP slot rated by speed (2x, 4x, or 8x). In the last few months, Intel has begun to offer a new slot design called PCI-Express that on paper can operate four times as fast as the fastest AGP slot. However, at the currently available technology, no video adapter card requires that much extra speed. [For more information ...|video]
  
 h3. PCI and PCI Express
  
 For a decade starting in 1985, PC adapter cards all plugged into the "ISA" bus. Then Intel came up with a better, faster PCI bus, which has dominated the last decade. The good news from such a long period of stability is that there are lots of fast, cheap, compatible adapter cards to upgrade your computer with an extra disk controller or a better audio system. The bad news is that ten years are up and it is time for a new I/O bus. The only part of PCI-Express that is similar to the old PCI bus is its name. It provides a much higher speed in a much smaller socket. However, although there are a few PCI-Express video cards available, there are no PCI-Express adapter cards. Systems will continue to need PCI slots for at least the next few years. [For more information ...|bus]
  
 h3. Ethernet
  
 An Ethernet adapter card connects an office PC to the corporate network. At home it connects several computers to each other for file sharing, and it allows all the computers to share a single high speed Ethernet connection over a DSL or Cable modem.&nbsp; [For more information ...|ethernet]
  
 h3. USB and FireWire
  
 To connect external devices (printers, scanners, disks, CD or DVD writers) to a computer there are two popular connection standards. USB 2.0 and FireWire provide full speed support for large numbers and a broad variety of external plug and play devices. [For more information ...|usb]
  
 Copyright 1998, 2008 PCLT \-\- _Introduction to PC Hardware_ \-\- H. Gilbert