The Hand-Me-Down PC
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The Hand-Me-Down PCFree Computer Ebook |
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Copyright 2005, 1996 by Morris Rosenthal
This book has been replaced in most usages by my latest book PC Repair and Troubleshooting. Click here to get there:-) Most people who buy a car are not automotive engineers. Yet the vast majority of us make comparisons between cars as a part of the buying process. If you have a lot of kids, you want a lot of seats. If you have a lot of tools, a pickup or van may be a good choice. Big motors usually pull more weight, turbo-chargers make it go faster. Cruise control and air-conditioning are luxuries for some and necessities for others. You don't need to be a musician to decide on a stereo and you don't need to know how a transmission works to choose between a manual and an automatic . When the car gets old, and the transmission shop wants $1000 to put in a rebuilt with a 90 day warrantee, the decision to invest the money or buy a new car often has as much to do with the condition of your bank account as with the overall condition of the car. The purpose of this chapter is give you a feel for how all the parts in a PC add up to make a working computer. Like automobiles, many models are built on the same chassis, with the most expensive loaded models costing more than twice as much as the stripped down economy version. There are many "after-market" enhancements you can make, some are "add ons" and some replace the original components. The expensive models have the potential to get you where you're going faster, and in more comfort. However, there are few fundamental differences between PCs and cars that makes buying and owning a PC a whole lot easier. One difference is that PCs are all built to standards such that their component parts, even across brands, are largely interchangeable. Another difference is that is that most of these parts are either commodities or or available from a single source only, i.e., you can buy memory or a floppy drive from any manufacturer, but Intel chips come from Intel Corporation and MS DOS comes from Microsoft. The System Box or CaseThere are two kinds of computer parts. There are things that go in the system box, and things that attach to it. The system box itself is either a flat metal box, with a couple buttons and lights on the front with at least one place to insert a floppy disk, or the same flat metal box stood on end. The flat box laying down is called a "desktop case" and the flat box standing up is called a "mini-tower." Big mini-towers that sit on the floor are called "towers." The system box has one power cord that gets plugged into the wall, and all sorts of connection points called "ports" for things outside the box to get plugged into. Two things that every computer will have plugged into ports are a keyboard and a monitor (TV display). Other things that are commonly plugged into ports on the system box include: a mouse, a printer, a telephone wire, a joystick, and speakers. The parts that get plugged into ports on the system box are often called "peripherals." Before we start to examine things that go in the system box, let's look at the box itself. The front of the system box is covered by a plastic face-plate, with several rectangular cutouts, a couple buttons and LEDs (lights), a key hole, and a power switch. The power switch is often on the side of the older desktop cases. The rectangular cutouts cover the drive bays, where floppy drives, CD ROM drives and hard drives are screwed in. The larger bays house 5 1/4 " floppy drives, CD ROM drives, and older hard drives. The small bays house 3 1/2" floppy drives and newer hard drives. The two push buttons, side by side, are labeled "reset" and "turbo." The reset button is for re-starting the computer if it stops responding to keyboard and mouse input. The turbo button switches the machine between its top speed, and a slow speed which is only useful for playing games or troubleshooting. On the high speed, the turbo LED should be lit. The power LED should be lit all the time when the computer is on, and the HDD LED would blink when the hard drive is being accessed. The buttons and the LEDs are for the benefit of the user. The computer will work fine even if they are hooked up wrong or broken. Inside the box is normally where the confusion begins. Here we have RAM, ROM, Megabytes and motherboards, drives and adapters. All of these things are necessary for even the most stripped-down computer, but they need no assembly beyond plugging connectors together and turning in the occasional screw. The cost of each part can be as high as a couple hundred dollars, or as low as $10 or $20. The first part we'll consider, the power supply, is usually purchased with the system box itself, and in some brand name machines, will have a unique shape (form factor). A unique and painful replacement cost goes hand- in-hand. Power supplies and system boxes are normally sold together, for a price between $40 dollars for a cheap mini-tower to $70 for a desktop and over $100 for a tower. The cheapest cases often have metal burrs inside that scratch unwary hands, and lack fit and finish. The Bare Bones SystemA bare bones system consists of a case, power supply, motherboard, CPU (brain) and memory. New computers are often sold to computer stores and other resellers as "bare bones" for a couple of reasons. One is the FCC (Federal Communications Commission) approval sticker that should appear on the back of every computer, certifying that it won't interfere with your neighbors TV or radio. Manufacturers will sell "bare bones" systems as FCC approved, although there is no guarantee they would pass the test with other parts added. Another reason is that screwing in the motherboard and connecting all the little lights and switches is a dreary job that most resellers are willing to pay a few dollars to avoid. We will take advantage of the "bare bones" approach and divide up the parts inside the system box into three categories: ."bare bones," "drives," and "adapter cards." The Power SupplyThe power supply, which is attached to the case with four to six screws, takes the 115volts of AC power from your wall plug, and turns it into the small DC voltages that all computer components operate on. The only continuos sound computers make when turned on is the power supply fan cooling the power supply. If the fan fails, the power supply will quickly overheat and fail. The cost of a standard power supply, for both minitower and desktop cases, is around $35. Old fashioned "AT" type power supplies, with a large paddle switch on the side, run over $50. The main figure of merit for power supply connoisseurs to boast about is their power output, in watts. The standard, cheap, power supply delivers 200 watts, which is more than you'll ever need. The power supply performs two jobs insides the box. One is to supply power to the motherboard in a wide variety of voltages, and the other is to provide power to the drives. The MotherboardAll of the parts that go into building a computer have a direct connection to the motherboard. The motherboard, besides serving as the traffic cop for routing information to all the parts, also serves as the home of the brain (CPU) and the memory (RAM), which fit into special sockets. A lot of terminology is used to describe different flavors of motherboards and their capabilities, but most variations have little real impact on the user. The main point to get is that the motherboard is where the software you will run on your computer actually executes, as the brain works with the information stored in the memory. Motherboards are often sold with the brain (CPU), and a new generation of motherboard must be designed for each new CPU (386, 486, Pentium) that's released. A 386 motherboard, with CPU, has no value on the market, while a new 486 motherboard with CPU might sell for up to $75 dollars. Pentium motherboards, with CPU, range from $100 to $1000 dollars, depending on the exact model (Pentium, Pentium MMX, Pentium PRO, Pentium II). CPU (The Brain)The vast majority of all CPUs mounted on PC motherboards from the beginning of time (the early eighties in this case) are manufactured by Intel. Other companies that have tried competing, including NEC, Texas Instruments, Cyrix, and Motorola, which makes the CPUs for Apple Computers. However, the only CPUs besides Intel that you're likely to find inside a hand-me-down PC are manufactured by AMD (American Micro Devices). Fortunately, they follow the same nomenclature, so I will usually omit the manufacturer and refer to CPUs generically as 386s or 486s. The primary figure of merit for a CPU is the clock speed, measured in MHz (Megahertz). To understand speed with which CPUs operate, let's compare them to alarm clocks. Alarm clocks come in two basic types; digital and analog. An analog alarm clock motor runs directly off the 115 Volt, 60Hz AC power from the wall outlet. Through a series of gears, like an automobile transmission, the alarm clock motor moves the second hand around the face once a minute, the minute hand once an hour, and the hour hand, twice a day. Those of us with a cheap analog alarm clocks and good ears can hear the alarm faintly building up before it goes off. That's because time, in the analog world, is continuous, so things never happen "all at once." A digital alarm clock displays the time in Arabic numerals, and changes the time displayed once a minute. If the alarm is set for 6:30 AM, when the clock changes from 6:29 AM to 6:30 AM, the alarm starts to beep. In effect, there has been a step change, an "all at once," and there are no faint warning beeps before the alarm sounds. CPUs are digital. The CPU clock speed tells us how many step changes, or operations, the CPU will make in one second. For example, a 386DX-25 CPU does 25 million operations per second. A 486SX- 25 CPU also does 25 million operations per second, while a 486DX/4-100 CPU does 100 million operations per second. CPUs all do millions of operations per second, expressed as "MHz," so we only need to comprehend the smaller number, 25, 66, 100. The speed of the CPU isn't the only thing that determines how fast the computer runs your software (imagine putting a race car engine in a truck), but the higher the number, the faster the machine. There are three other parts to the nomenclature, which you may have noticed above. First is whether we have a 386 or a 486. CPU manufacturers improve their chips with each generation, and the 486 is required by many newer software packages. The 486 replaced the 386, just as the 386 replaced the 286, which was the CPU in the IBM PC-AT. Don't pay for a 386. Another part to the nomenclature is the "DX" or "SX" part, and the last bit is the "4" that appears in the 486DX/4-100. With both 386 and 486 CPUs, the DX does complicated math (engineering calculations) better than the SX. Some software may require that you have a DX type CPU, or that you buy another CPU like chip known as a math co-processor to compensate. Just remember DX is better than SX, and don't buy a machine with an SX CPU unless it comes with a real nice monitor you can use on your next machine. The "4" that appears in 486DX/4-100 or the "2" in 486DX/2-66 tells us that while the CPU runs at the stated speed, 100 or 66, it talks with the motherboard it's plugged into at a lower speed. That means it can work very quickly with information held in the CPU, but if it has to go out and get something from memory, things slow down. Current CPU speeds in new Pentium PCs range from 166MHz (a low end Pentium MMX) to 300MHz for a high end Pentium II. RAM (The Memory)Memory is what the CPU shuffles through in order for the software to accomplish anything. The CPU never looks directly at the information on your floppy disk or your hard drive. This information is copied into memory by one of the traffic cops on the motherboard. The CPU then reads this information from the memory and acts on it. Random Access Memory (RAM) is called by this name because the CPU can get information from any location in the memory in much less than a millionth of a second. Even picking spots at random, the retrieval speed remains unchanged. This is very different from the case with a floppy drive. Bits of information stored next to each other on the floppy can be read quickly, while bits which are recorded a couple inches away on the disk take much longer to retrieve, actual fractions of a second! Sometimes a "D" is added to the front of "RAM," which makes the word "DRAM." The "D" stands for dynamic, because the RAM actually forgets what it's holding if the mother board doesn't continually refresh (read and re-write) the information. Everything in DRAM disappears when the computer is turned off. Computers work with very small bits of information, intelligently known as "bits," which have to be combined together into larger clumps to make any sense. The basic clump used by computers consists of 8 bits and is known as a "byte." Memory size is measured in bytes, and more is always better. Since computers need huge numbers of bytes to do anything useful, the measure of a "megabyte," one million bytes, is used. Early 386 machines could limp by on 2 megabytes (MB) of RAM, but 4 MB is the minimum required to run Windows 3.X in a reasonable fashion. 4 MB works fine with most older software, but 8 MB is being required by many new programs. Very few DOS/Windows programs require 16 MB (the next possible increment due to the way memory is installed in most machines), but overall performance does improve with additional memory. Windows 95 can operate with 8MB, but many Windows 95 applications require 16MB, and 32MB is now standard on the run-of-the-mill new PC. Today RAM costs less than $5/MB, down from about $10/MB one year ago, and $35/MB in 1995. DrivesDrives provide the permanent storage for your computer. When the computer is turned off, all of the parts except for the drives are effectively wiped clean. Drives all use electric motors to spin disks or tapes, and require a power lead directly from the power supply. Most drives, like floppies, CDs and tapes, use a removable media that we slide into the drive on the front of the system box. Some special purpose drives (you'll rarely see one on a hand-me-down PC) sit entirely outside the system box and are connected by a cable to a special port, and these are called "external drives." Hard drives are sealed against the atmosphere, and have no removable media. These drives can rarely be seen from the outside of the system box, which is why manufacturers include a "HDD" LED (light) on the front panel to show when they are being accessed. The Floppy Drive.Floppy drives and floppy disks come in two sizes: the older, flexible, 5 1/4" disks and the newer, rigid, 3 1/2" disks. Floppy disks, which are read by a floppy drive, provide permanent, removable storage for your computer. The storage is permanent, because it is recorded in the magnetic material of the disk the same way that audio or video cassettes are recorded. As long as you keep the disks away from big magnets and don't spill coffee on them, they'll hold the information for a couple years. Several different formats for floppy disks exist, which describe how much information can be recorded on them. Old floppy drives only read and write the low capacity, or low density formats. These old "double-density" formats are measured in KB (thousands of bytes); 360KB for the Double Density 5 1/4" disk, and 720 KB for the Double Density 3 1/2" disk. New drives, with High Density floppies, record 1.2 MB on a 5 1/4" disk and 1.44 MB on a 3 1/2" disk. The drives are cheap. A brand new 1.44MB drive costs about $25, a 1.2MB drive about $35. There is no reason for buying or using a 1.2MB (5 1/4") drive, unless you are stuck with a bunch of old disks filled with information. Even then, your best bet would be to copy them onto newer disks. Let me give you a tip about buying disks, which can be confusing. 1.44 MB disk, hopefully the only kind you would be out buying, is labeled 3 1/2" HD. 720 KB disks are labeled 3 1/2" DD. Both types are double sided (DS), the information is written on both sides. 1.2MB disks are labeled 5 1/4" HD, and 360KB disks, if they are still sold, are labeled 5 1/4" DD. Again, both are double sided, and the description is sometimes run together as DSDD, in the case of the 360KB case. Single sided, single density disks exist only in museums. Hard DrivesNow we're getting to the real storage. The hard drive is essentially several non-removable rigid floppy disks stacked together with a drive built around them. Because the disks are rigid, the read/write heads can be positioned much more accurately, allowing more information to be written (higher density). Another advantage is the disks can spin much faster, thousands of RPM (Revolutions per Minute). As a result of higher recording density and faster spinning, hard drives can write and retrieve information much faster than floppy drives. The most important measure associated with a hard drive is the capacity, how many megabytes it can store. Hard drives being sold today can hold over 1000 floppy disks worth of information, but our older drives have a more modest capacity. About the smallest drive you'll find in an old 386 is a 40MB drive, which could just about hold DOS and Windows with a couple small programs. Drives up to about 500 MB are commonly found in older PCs, and some machines will have a second drive installed. Pricing for old drives is irrelevant, since they quickly dissapear from the market when new drive prices fall. About the smallest hard drive commonly available today is the 800MB drive for $100. A 1000 MB (or 1 gigabyte) drive costs about $125, and a 3.0GB drive goes for less than $240. Hard drives are very reliable (much more so then floppies) and most have an operating life exceeding five years. However, if you have important information on your hard drive, say your checkbook or your unfinished novel, it's always a good idea to make a fall-back copy onto a floppy disk. This procedure is known as "backing up." Store the backup disk(s) away from the computer, so in case of fire or theft, you still have your copy. CD-ROM DrivesCD drives are relative newcomers to PCs, coming into common use about five years ago. CD drives made possible the delivery of huge software programs and games to the user that would otherwise require hundreds of floppy disks. CD discs are very cheap to mass manufacture at about 60 cents each, and have tremendous shelf life, over 100 years. All CD drives are capable of playing regular music CDs, and have a headphone jack on the front of the player. If the system box contains a sound card, the music can be amplified and played out of speakers. CD discs come in one size only, with a maximum capacity of about 680 MB. The main comparison between CD drives is the transfer speed, how fast they can hand information to the motherboard to be placed in memory. This is expressed as a multiple, 2X, 3X, 4X, 6X and so on of the original CD drive transfer speed, which was the same as that of a stereo CD player. While any speed CD drive is better than nothing, 2X (double speed) is the minimum needed for multimedia, and the cost of 6X drives is already down under $50 (if you can find them), so the slower ones are no longer sold. The current state of the art CD drive is the 24X, which still costs over $100. DVD drives are just coming onto the market with in their 4.0GB incarnation, and are discussed in the printed book. Tape Drives Many older PCs are equipped with tape drives for backing up the information on the hard drive. The most common drives had a capacity of 120 or 250 megabytes, stored on a removable tape about half the size and twice the thickness of an audio cassette. These one-sided tapes are easily recognized by the thick metal bottom of the cartridge that helps conduct away heat. Some more expensive or obsolete drives use tapes as small as a telephone answering machine cassette or as large as a VHS cassette. Tape drives in individual computers have gone out of vogue for two reasons. First, they proved less reliable than the hard drives they back up. Second, as hard drive capacity skyrocketed, the cheap tape drives required several tapes (and hours) to back up the data. Another reason is that most companies have installed networks, which allow the administrator to backup individual computers onto a single, fast tape drive at a central location. Second-hand tape drives have no market value, and are often "orphans," i.e., the tapes are no longer available. AdaptersAdapter cards which plug into the motherboard are what give PCs the tremendous flexibility to do all of the jobs we can think up for them. As computer technology has evolved, the sockets on the motherboard, called "bus slots," into which the adapter card are placed, have evolved as well. The latest adapter cards used in Pentium computers can move four times as much information in a single effort as the older cards used in 386 computers. Most 486 computer motherboards sport a few slots which fall in- between in this evolution, allowing use of adapter cards which move twice as much information at a time as in 386s and half as much as in Pentiums. The classification of these adapters is important if you are buying replacements, and they go as follows: 16 bit adapter (286 motherboards and higher), VESA adapter (486 systems), EISA adapter (some 386 systems and higher, very expensive) and PCI adapter (Pentium systems). All motherboards, including the newest Pentiums, leave a couple old fashioned 16 bit slots (sometimes even 8 bit slots!) for compatibility with old technology. The standard motherboard can support (has space for) six or seven adapters to plug into the bus. Video AdaptersThe video adapter performs the job of the cable box or the antennas on your TV. It takes the information the motherboard tells it to display and generates the signals that the monitor understands. In the case of old video adapters; Hercules, CGA (Color Graphics Adapter), EGA (Extended Graphics Aapter), this was a digital code. Do not pay for a computer with this type of adapter or monitor. The new generation of adapters, VGA (Video Graphics Adapter), operate more like a traditional television, providing the monitor with color (Red, Green, Blue - RGB) information and some timing signals. There are several distinct levels of performance associated with VGA adapters, namely how many colors they can display at one time, how much information they can squeeze onto a screen, and how often they update the information. How fast the different video adapters can refresh the monitor is dependent on both the adapter and the monitor, and is set aside for the monitor discussion. VGA adapters come equipped with their own RAM for temporarily storing what will be drawn on the monitor, and the amount of RAM usually corresponds with the overall performance of the adapter. The brand of VGA adapter, and the amount of RAM it carries in kilobytes (KB), is usually the first thing displayed on the monitor when the computer is turned on. VGA Adapters with 256KB RAMVGA adapters with 256KB RAM are no longer sold. These adapters limit even the most expensive monitors to displaying 256 colors at VGA screen resolution. By VGA screen resolution, we are talking about the number of pixels (separate points) the monitor uses to fill the screen. VGA resolution uses 640 pixels horizontally across the monitor, and 400 pixels vertically, up and down. This compares well with broadcast television, which uses 512 pixels horizontally by 384 pixels vertically to fill up your TV screen, which is usually much larger than your monitor. For the math lovers crowd, you can multiply 640 and 400 together, coming up with 256,000, or 256K. These 256K pixels require one byte of memory each, which is where we get the 256KB of memory. One important note is that the video adapter requires special software called a "driver" to be installed on your computer for it to work to its highest potential. Without the driver installed, Windows and other software will only display 16 simultaneous colors, instead of 256. SVGA Adapters with 512KB RAMSVGA adapters (you caught the "S" sneaking in front of the VGA) are capable of displaying "Super" VGA resolutions, beyond the 640 by 400 resolution of plain VGA. As you can guess, more resolution means more pixels, and more pixels at one byte of memory per pixel means more memory. SVGA adapters can display 800 pixels horizontally by 600 pixels vertically on the screen. Or, at two bytes of memory per pixel, they can still display regular VGA resolution. The extra byte per pixel at regular VGA resolution lets the adapter display 256 multiplied by 256 equals 64,356 colors at one time. Over 64,000 colors is enough to make most images appear as clear as photographs on a good monitor. SVGA adapters are a minimum requirement for multimedia software for this reason, the ability to display near to "true" color. Some people will use the SVGA adapter to display the 800 by 600 pixel resolution instead, which fits almost twice as much information on the screen in one shot. The penalty for doing this is that everything appears proportionally smaller (remember, the size of the monitor hasn't changed), and only 256 colors can be displayed at one time. These adapters are sold in the $30 to $40 range. Again, software from the manufacturer controls how the SVGA adapter operates. Video Adapters with 1MB RAM and BeyondThe standard video adapter sold today comes with 2MB (2048KB) of video memory, and many 486 PCs were equipped with these cards. With double the memory of the 512KB adapters, they can send the monitor over 16 million colors to be displayed simultaneously at VGA resolution. This creates a picture perfect image know as "true color." Likewise, there is now enough memory per pixel at SVGA resolution to display over 64,000 colors simultaneously. Most of these adapters can operate at even higher resolutions, displaying 256 colors at 1024 by 768 resolution, or 16 colors at 1280 by 1024 resolution. These higher resolutions are normally only used by artists or computer draftsmen who have large monitors (over 17") and buy video adapters with 2MB of memory or more to allow them to display more colors at these super high resolutions. Input/Output (I/O) AdapterBefore we even begin the discussion of the I/O adapter, we must note that in almost all 386 and 486 computers, the functions of this card have been combined with the disk controller functions into a single adapter, the SIDE adapter, which will be discussed in the next section. The I/O functions we discuss here operate exactly the same way when combined into the SIDE adapter. The I/O adapter provides several ports, through which the computer communicates with the outside world. There are three types of ports provided; serial communications, parallel communications and the game port. Two serial ports are provided, normally called "Com1" and "Com2," one parallel port called the "Printer Port," and the game port, normally used to connect a joystick for arcade type games. Nearly all computers will have a mouse (pointing device) connected to the Com1 port, and almost all printers sold will work when hooked up to the printer port. The second serial port normally goes unused, unless an external modem (connects your computer to the world through a telephone lines) or some special equipment is purchased. An I/O adapter costs less than $10.
SIDE AdapterIn the early Nineties, a type of hard drive using Intelligent Drive Electronics (IDE) began to take over the PC market. An intelligent hard drive allows for a simple controller, which really just ties the drive directly to the motherboard. At first, these hard drives shipped with an adapter known as an IDE Paddle card, which doubled as the controller for the floppy drives. Ribbon cables, many wires molded into a flat plastic cable, connect the adapter to the hard drive(s) and the floppy drive(s). Manufacturers soon figured out there was enough room on the adapter to add all the functions of the I/O adapter, and created the Super IDE (SIDE) adapter. These adapter cards sell for less than $15, which makes them the least expensive component in the box. Unfortunately, since these adapters are so "low-tech" and inexpensive, the quality tends to be poor, and they are the weakest link in most computers. I once sent a new technician out for her first afternoon of field service with three new SIDE adapters, with which she was able to repair three different computers. SIDE cards are also liberally sprinkled with jumpers, a type of switch that can select between two options. These jumpers can enable and disable the different functions, and in some cases, change the locations of the ports (i.e., Com1 becomes Com3 or Com2 becomes Com4). Other AdaptersA video adapter and a SIDE adapter are the minimum number of adapters required for a PC to operate. Millions of computers complete their life cycle with no additions to these two basic adapters. If you don't have any additional adapters, you can skip down to "Outside the System Box" at this point. There are literally hundreds of other adapters available for PCs, most of them designed to let the computer talk to a specific piece of equipment in a laboratory or on a shop floor. While your hand-me-down PC might contain a left over adapter from some obsolete system, guessing at what it might be is beyond the scope of this book. In the next few paragraphs we will cover the more common adapters you might find in a hand-me-down PC, or buy, but a final word about unknown adapters. Leave them where they are, and don't start plugging things in unused ports at random to see if they do anything. In other words, "If it's not broke, don't fix it." Internal ModemAbout the most common and most useful extra adapter you can have in your PC is an internal modem. A modem is a device that gets plugged into a telephone jack that enables communications between your computer and other computers. These other computers could be at work, at your bank, or the gatekeepers (servers) on the Internet or the World Wide Web. Like most computer parts, modems have evolved to communicate faster and faster over the last ten years. Because of the premium prices commanded by faster modems, most older computers will come with slow modems. Modems are categorized by their line data rate in bits per second (bps). The slowest modem you'll find in an old 386 will run at 1200 bps, compared to the newest modems in Pentiums which run at 33,600 bps (even faster using one way digital links - up to 56,000 bps). Modems in 386s and 486s can be at either extreme or fall anywhere in-between. The important cut off number, 14,400 bps, is known as a "fourteen four," and this is the minimum speed for a modem to achieve acceptable performance on the World Wide Web. Fourteen-four internal modems cost about $20, twentyeight-eight modems around $40. 33.6K modems begin around $50, and 56K modems around $100. Most modems are also capable of sending and receiving faxes, but people with a serious amount of faxing to do will find a regular paper fax far more convenient. Sound CardsSound cards are adapters that perform at least three functions. Two of those functions are complimentary; converting analog sound from a microphone or stereo jack into digital computer codes (A/D) and converting the computers digital codes for sound back into voice or music, that is played back through speakers (D/A). They provide enough amplification so that a CD drive played through the sound card will provide enough power to drive the speakers. Most sound cards also have a ribbon connector for connecting CD drives that can't be connected to a different adapter. Musical Instrument Digital Interface (MIDI) sound allowed the card to create instrumental sound based on "cues," which take less than 1% the storage space than actual recorded music. Newer cards also support the Wave Tables, which use pre- sampled selections of actual instruments to produce a much richer sound than MIDI. Sound cards, like everything else, have evolved since their introduction in the early Nineties. The original successful card was the Sound Blaster from Creative Labs, and most sound cards manufactured since guarantee "Sound Blaster" compatibility. The oldest generation, called "eight bit" cards, are better than nothing, but should not be purchased. "sixteen bit" cards are capable of recording and reproducing sound as accurately as your stereo CD player. However, high fidelity recording also depends on having a system fast enough to take the recorded sound from the sound card and move it to the hard drive without any interruptions. A "sixteen bit Sound Blaster Compatible" goes for around $30, while a real Sound Blaster from Creative Labs cost about $50. More expensive sound cards with recording studio type software can cost hundreds of dollars. Network AdaptersFew of us have LANs (Local Area Networks) in our homes, but cost is no longer the reason. Early network adapters costs hundreds of dollars apiece, but while some brand names still hover around the $100 mark, reliable network adapters for all types of networks can be purchased in the $30 to $40 range. Special network software which once had to be purchased separately now comes as part of the Window for Workgroups or Windows 95 software. LANs allow information to be passed from computer to computer about 1000 times faster than by a modem connection. There are at least a half dozen types of LANs in use, with names like Token Ring, Ethernet and Arcnet. The most common LANs, outside of big corporations, variations on the Ethernet standard; 10Base 'T', which uses twisted pair telephone type wire, and Thin Ethernet, which uses coaxial cable. The $30 to $40 adapters mentioned earlier support both types of LANs. Small Computer System Interface (SCSI) AdaptersSCSI adapters, pronounced "scuzzy," are high performance, general purpose adapters for connecting the motherboard to a variety of drives and devices. Most high performance hard drives are SCSI drives, along with CD Recorders (CDRs), some CD players, and quality tape drives. SCSI adapters also support connection to external devices, including portable versions of all of the above mentioned drives, and other devices like scanners which digitize (change into digital computer codes) documents and photographs. A single SCSI adapter can support up to seven different drives and devices simultaneously. Low performance SCSI adapters start around $50, while the best adapters with controlling software cost up to $500. SCSI adapters also support floppy drives, so some systems will have a SCSI adapter and a I/O adapter instead of a SIDE adapter. Video Capture CardsThese special adapters are used to capture single frames or real motion video from a VCR, Video Camera, or other video source. Prices for "Frame Grabbers," which capture a single picture, start under $100 while decent motion video capture cards start at a few hundred dollars. Capturing quality motion video is extremely dependent on the system, a fast 486 with a special A/V (Audio/Visual) hard drive is the minimum requirement, and probably won't produce anything good enough to be used in a saleable product. Video capture and edit workstations used by professionals may be based on PCs, but typically cost well over ten thousand dollars. Things Outside the System BoxThere are two things that attach to every system box to make it a working PC: a keyboard and a monitor. Modern software is easier to work with if we add a third item for pointing at things on the monitor screen, a mouse. The next most common thing to attach to the system box is a printer, followed by external modems, external drives, scanners, digitizers, and other special purpose accessories. In the chapter on what you can and can't do with your hand-me-down PC, we'll look at some combinations of equipment for different professional tasks. Things that get plugged into communications ports on the system box are called "peripherals," and are almost never manufactured by the same company whose name goes on the system box. Sometimes, the same company name appears on the peripherals because they pay the real manufacturer to put it there. As with clothing, mattresses, and other purchases, you can often buy the exact same part without the brand name for a fraction of the cost. KeyboardsThe keyboard is are an area where preference for "feel" varies greatly from person to person. Most people will be comfortable with the first keyboard they work on, and feel there is something wrong with any new keyboard, until they get used to it. Most keyboards sell in the $15 to $20 dollar range, including my personal favorite for reliability and feel from Mitsumi Electronics, over 1000 sold without a single failure. In my experience, extremely expensive keyboards (almost $200 retail) manufactured by one of the world's largest computer companies, have a failure rate of about five percent per year. Keyboards receive power from the motherboard, so there is only one connection to make. The newest keyboards on the market feature "V" shapes for ergonomic positioning of the hands, and wrist rests and other devices to combat repetitive use injuries are available for people who work for extended periods of time typing every day. MonitorsMonitors come in a dizzying array of sizes, capability, and prices. To simplify the discussion, we will stick to VGA monitors and better. Information about old "TTL" type monitors is contained in the troubleshooting chapter. The least expensive SVGA monitors start at around $160. Many 386s and some 486s were shipped with VGA (not SVGA) monitors, not capable of displaying higher resolutions even with a more expensive video adapter. Unfortunately, the manufacturer's labels on the back of the monitor rarely identify the capabilities of monitor, beyond giving a model number. Try to obtain the instruction booklet with any second hand monitor purchase, otherwise you'll have to trust the seller. Monitors that display VGA resolution only, and "paper white" VGA monitors are no longer sold and are rarely worth repairing. If you already own a monitor and are happy with it, you might want to skip the next section which unavoidably gets a little technical. Screen Size.Monitors, like television sets, are measured diagonally, from two opposing corners of the picture tube. The standard monitor size is 14," and prices rise rapidly with increasing screen size. Very large monitors can measure 21" diagonal or greater, weigh over 80 pounds and cost more than $2000. Manufacturers of monitors, like manufacturers of some clothing items, are not entirely consistent with their measuring schemes. Some measure parts of the picture tube that are hidden behind the plastic bezel of the monitors casing, and others simply don't allow the screen size to be adjusted to anywhere near the edges of the bezel. This has led to an unofficial measurement known as "viewable area," measured diagonally, which describes how large a picture you can actually see. For example, one 17" monitor may have a viewable area of 16 1/2," while another may have a viewable area of 15 1/2." One recent innovation is the "flat screen" monitor, which doesn't have the curved face of the standard picture tubes in most monitors and televisions. Flat screens look a little better than standard monitors, and cost a little more. Interlace and Horizontal FrequencyThe two factors that control how "solid" or "flicker free" your monitor is are the whether or not the display is "interlaced" or "non-interlaced," and the horizontal frequency, which controls how many times per second the screen is redrawn. Monitors, like televisions and movie projectors, flash a series of pictures at us, which our eyes and brain merge into a solid image. How many images per second are required to create a really "solid" looking picture varies from individual to individual, but the minimum number of times per second (frequency) an image is displayed by any modern monitor is 60 per second (60Hz). The cost of the electronic components that control the picture tube go up in price as they go up in speed. One trick that allowed monitors with slower electronics to draw SVGA resolution images without excessive flicker is "interlacing." When an image is interlaced, the monitor draw the entire image more than 60 times per second, but skipping every other line. On the next redraw, it does only the lines it skipped. The result is that the entire image appears less bright and a little flickery to some people, while others don't notice. For about $20 more, a non-interlaced (NI) monitor will be capable of drawing the whole image every cycle. Interestingly, most clone builders never bothered properly configuring the software and the video adapter to work with the NI monitors, thus buyers didn't get the benefit they paid for. Even with an NI monitor, some people who stare at monitors all day long, especially under artificial lighting, see flickering or get dizzy by the end of the day. The way to make the picture appear even more "solid" is to run up the horizontal frequency to 72Hz or 75Hz. The increase in price to the video adapter is trivial, in fact most 512K and 1MB SVGA adapters can already handle 72Hz, known as the VESA frequency (VESA for the Video Electronics Standards Association). The real challenge for both adapters and monitors is maintaining the higher horizontal frequency at screen resolutions beyond SVGA. Why does it matter? Well, for a VGA screen, the monitor electronics must draw 400 lines each 640 pixels long during each cycle. For each pixel in each line, the video adapter must tell the monitor how much of each primary color, red, green and blue, to light up for each pixel. At SVGA resolution, 300 lines each 800 pixels long must be drawn in interlaced mode, and 600 lines of the same length in noninterlaced mode. Raise the resolution higher, than tell the electronics they have to redraw the whole image 72 or 75 time per second, and you've got some hard working transistors on your hands. Resolution and Dot Pitch (DP)How "sharp" an image looks is determined by how many pixels (dots) the image is made comprises, and how large the dots are. The best combination to create a really sharp image is a high resolution with a low dot pitch (DP). Resolution depends on the video adapter, software and monitor all working together; the dot pitch depends on the monitor alone. Manufacturers use a couple of different approaches to defining dot pitch, but it basically defines how large each pixel or dot on the screen ends up being. Fourteen inch monitors should have a .28 DP, while larger monitors range from DPs of .25 to .31. A 14" monitor with a high dot pitch, say .39, is cheaper, but image definition is poor. The trade off on resolution is a given image displayed at two different resolutions will appear appear sharper at the higher resolution, but larger at the lower resolution. Most people run their 14" SVGA monitors at VGA resolution for this reason, although it's nice being able to switch to a higher resolution when you need to. If you want easily readable screen fonts (characters) at SVGA resolution, consider a 17" monitor. Mice and Other Pointing Devices.Mice can be purchased for anywhere between $5 to $100. The mouse you receive with any system bought as a whole is going to be the $5 model. Unless you do a lot of desktop publishing or other graphics work and want a special "feel" or extra control software with the mouse, the cheap version works fine. A mouse is normally connected to the system box via a Com port, normally Com1, but there are two other methods. The first method, used in brand name machines only, is via a special mouse port. This is normally located next to the keyboard connector. The second approach, popular in the early nineties, is called a "bus mouse." In this approach, the mouse requires its own adapter card, and is plugged into a special port on this card. Other pointing devices include penpointers, trackballs and joysticks, like those used in video games. Artists and draftsmen who need to position lines down to the thousandth of an inch or lower, use digitizer pads, which start around $200. The user either draws on this pad with a special instrument like a pen, or uses a mouse like device that sports a cross hair for precise positioning. PrintersPeople have been experimenting with ways to reproduce words since Guttenberg printed the Bible over 500 years ago. That's the long way of saying there are at least a dozen technologies that have been widely used at one time or another for computer printers. We'll limit our consideration to the big three; Dot Matrix, Laser and Inkjet. All three types of printers are available as color or black and white, with color inkjets representing the happy medium between price and quality for color printing. Prices range from $100 for a cheap dot matrix to over $10,000 for a production color laser. Each printer has a niche it fills best, but if somebody offers you one of the above for free, take the laser. Dot Matrix PrintersDot matrix printers have been around for over 25 years, so most of the bugs have been worked out. The two characteristics that describe dot matrix printers are the number of pins in the print head , 9 pin or 24 pin, and the width of the carriage; "narrow" or "wide." The cheapest printer is the narrow carriage 9 pin, and the most expensive is the wide carriage 24 pin. The width of the carriage simply refers to how wide the paper path is, where the narrow carriage handles the standard 8 1/2" by 11" paper. The number of pins determines how close to "letter quality" the printing will look. The dots in the individual letters printed by a 9 pin dot matrix will be obvious, while a 24 pin printer on its slow "near letter quality" setting will produce much nicer print. The print quality of any dot matrix printer can't compete with that of inkjets or lasers, but they maintain a market niche where carbon copies or labels are used. Dot matrix printers normally come with both tractor and friction feed, chosen by a lever on the side. Tractor feed uses paper with holes along the edges for sprockets to pull the printer, while friction feed works like an old fashioned typewriter. Dot matrix printers are also rated by their speed in Characters per Second (CPS). The CPS in draft mode (not very pretty) is always much higher than the CPS in "near letter quality" mode. The consumable (computer lingo for a part requiring regular replacement) for dot matrix printers is the ribbon cartridge, which can cost between $3 to $20 or more. Expensive dot matrix printers called "line printers" are used for jobs like addressing bills or making out checks and can cost thousands of dollars. Inkjet PrintersInkjet printers are the newest addition to the printer family, and operate by shooting a stream of ink drops at the paper where they rapidly dry. Older model black and white inkjets can be had for around $125 while color models start around $200. All inkjets suffer from being slow, often turning out less than one page per minute. The advantages that inkjets hold over dot matrix printers is their ability to turn out good looking output, including graphics. The more expensive color inkjets can do a pretty good job with photographic images when printing on specially treated paper. The consumable for inkjet printers in the ink cartridge, which averages about $20. The inkjet market, both the printers and the consumables, is dominated by Hewellet Packard, which also has the lions share of the laser printer market. Laser PrintersLaser printers operate along the same lines as copying machines, except they have a lot fewer moving parts and are much more reliable. The two measures of performance for a laser printer are the number of dots per inch (dpi) and the number of pages per minute printed (ppm). Older lasers printed 300 dpi, which produces much better print than any dot matrix or inkjet. New lasers can print at 600 and 800 dpi, which is noticeably sharper when viewed through a magnifying glass. A slow laser printer will average about 4 ppm, middle of the road lasers manage 8 ppm, and expensive shared lasers used in office settings often print over 20 ppm. Cheap lasers without paper trays start under $400, a decent office quality laser costs about twice that amount. Options that add to the functionality and expense of a laser are PostScript compatibility, a software enhancement developed by Adobe that is required by some desktop publishing and artists software, and additional RAM for temporarily storing the images to be printed. The main consumable for laser printers is the toner cartridge, costing any between $10 to $200 dollars, depending on the life span and print engine. Image drums, which start around $100 for rebuilts to a couple hundred dollars for various new models, have longer lifetimes than toner cartridges, but also require occasional replacement. Recycled replacements are available at savings. Pricing and lifetime of laser consumables should be considered when comparison shopping laser printers. ScannersScanners are used to digitize (change into computer codes) photographs, artwork and documents. The resulting digitized image can be used to display the original on a monitor, reproduce it on a printer, or in the case of documents containing typed quality words and numbers, to read them. Changing the image of a document into actual words and numbers that can be used in a word processor or spreadsheet is called Optical Character Recognition (OCR). Scanners see images as either color or "gray scales," which convert the image into shades of gray varying from white to black. Color scanner prices vary from a couple hundred dollars for hand held roller scanners to tens of thousands of dollars for commercial models in the publishing industry. The most popular models are "flat bed" scanners, where a sheet of paper or photograph is laid flat to be scanned. A decent flat bed color scanner costs between $150 to $600, and comes with software and an adapter card. Inexpensive gray scale scanners lost out to color scanners when the prices came down, and don't really have any value in the second hand market. High end gray scale scanners, costing from several thousand to almost one hundred thousand dollars are used for processing large numbers of documents for archiving or OCR. The most expensive of these can scan over 100 pages per minute, compared to the one or two pages per minute achieved by inexpensive flat beds. Scanners use the same "dots per inch" dpi figure used by laser printers. Most scanners are capable of scanning at resolutions from 75 to 300 dpi, according to software settings. New scanners, even inexpensive models, can scan up to 600 dpi, and produce images that appear to be 1200 dpi using software tricks. High resolution scanning is important for photographs or artwork that will be reproduced later, but most OCR works fine at 200 dpi. Color scanners also have graded ability to reproduce colors expressed in bits of depth. Any newer scanner will manage 24 bits deep, while 30 bits deep or higher offers more accuracy and control. Most people who aren't professional artists or publishers will be happy with a $400 flatbed scanner that offers 24 bit color and 300 dpi. Pen PlottersPlotters are generally used by draftsmen or engineers to produce blue print type drawings or to graph measurements on taken by scientific instruments. Plotters draw with one color pen at a time, but are usually equipped with eight different colors. Desktop plotters draw on standard stationary paper sizes, while free standing floor models can handle all the blue print sizes (A,B,C ...). The only consumables are the pens, which are replaced or refilled on at a time. Plotters are connected to one of the communications ports on the system box, normally Com2, with a serial cable. Speakers and MicrophonesSpeakers, which require the presence of a sound card in the system box to be of any use, can be a little different from the speakers on your stereo. In order to play music at a reasonable volume from your sound card, you will need to run the output through an amplifier, or purchase amplified speakers. Some amplified speakers come require batteries, others come with a transformer that can be plugged into a wall outlet. Good amplified speakers, costing between $20 to $100, can make the CD player in your computer sound like a stereo, and add tremendously to the multimedia experience. Cheap speakers often come free with the sound card, but their volume is limited to a level around spoken conversation, and the fidelity is terrible. The microphone supplied with most sound cards works well enough, but is usually the clip on type.
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