Basic Computer Hardware
System Board
The term system board can be used to describe any number of circuit boards that make up the internals of your computer, but it is used most often to describe the motherboard. The motherboard is the main board in your computer that contains the BIOS chips, RAM, I/O ports, and CPU. This board maintains the electrical pathways that enable all other components to communicate with each other.
In some computers, you will hear the term daughter board used. A daughter board is a board that contains some of the chips that should have been put on the motherboard, but were not�perhaps due to space limitations or other reasons.
Power Supply
The power supply does exactly what its name suggests: supplies power to the rest of the components in the computer. The power supply takes 120 volts or 240 volts (depending on the country you are in) from your building and converts it to output ranging from 5 volts down to 1.5 volts. It contains a number of leads that supply different voltages for different types of devices (such as floppy drives and hard drives).
Processor/CPU
The processor is the �brains of the organization,� so to speak. It has been designed to do very few things, but do them extremely fast. The processor performs a limited set of calculations based on requests from the operating system and controls access to system memory. Processor speed is measured in several different ways, including clock cycles, Megahertz (MHz), or millions of instructions per second (MIPS). Either of these measures will give you an estimate of the processor�s power.
The speed of early processors ranged from 4�8MHz, while today�s processors have broken the Gigahertz (GHz) mark.
Memory
RAM (Random Access Memory) is the computer�s primary working memory. The OS (Operating System) controls the computer�s functions. When the OS loads, it loads into RAM; when applications load, they load into RAM; when you open documents, they load into RAM; and when you need to send output to your monitor, the output is loaded into RAM before it hits your monitor.
RAM is used in many areas of your computer, and in many different forms. It is used by the base OS in one big chunk that most people think of as RAM, but it is also implemented as processor cache (L1 and L2), video RAM for your video card, and any number of components that claim to have caching.
RAM speeds are usually measured in nanoseconds. One nanosecond is a billionth of a second.
There are many delivery forms for RAM. These include DIMM and SIMM packaging.
Firmware
It is human nature to want to classify everything we see or work with into categories. Many of these categories seem very distinct until something comes along to challenge our opinions, and then the waters become murky. Take the subject of hardware and software, for example, which at one time were thought to be distinct and separate entities. Software is programming code that is stored on your disk, or some other form of media. Hardware refers to the physical components�boards, peripherals, and other equipment�that make up your computer. Firmware fills in a middle ground between these two, where the distinct line begins to disappear.
Firmware is programming code (software) that is contained in or stored on the IC (Integrated Circuit) chips (hardware) on your computer. This combination of hardware and software makes up the BIOS on several different devices, with potential settings stored in CMOS.
BIOS
BIOS is short for Basic Input Output System. The BIOS is actually software that is stored in a ROM (Read Only Memory) chip on your motherboard. Most systems today use a Flash EPROM (Erasable Programmable ROM) so that the user can update them.
The BIOS is responsible for controlling or managing the POST (Power On Self Test), the boot process, and the interaction of components on the motherboard. These are all low-level processes that the BIOS is responsible for, but still extremely important to your system.
CMOS
CMOS is short for Complementary Metal-Oxide Semiconductor, which is the type of manufacturing process that creates most integrated circuits. This development process is used to create the following:
? High-density DRAM (Dynamic Random Access Memory)
? High-speed processors
? Low-power devices for mobile use
The term complementary refers to the fact that these chips use negatively and positively charged transistors (which complement each other) to store information.
Most RAM chips rely on CMOS technology to store information, but when discussing CMOS, you will probably be referring to the hardware configuration settings that are saved between reboots of your computer. These settings include:
? Hard drives and floppy drives
? Memory
? Keyboard
? Mouse
? Reserved resources (such as IRQ, I/O addresses, and DMA channels)
? Power on password
? Date
? Time
? ACPI (Advance Configuration Power Interface)
Storage Devices
Storage devices on your computer are responsible for storing data, such as the operating system, applications, and actual output of applications or user data.
Depending on the amount and type of data, there are three basic types of devices to work with:
? Floppy drives, including some of the high-capacity formats such as 120MB Superdisks
? Hard drives, including some of the removable cartridge drives such as SyQuest drives
? Optical drives, including CD-ROM and DVD drives
Any one of these formats will enable you to read data into your computer, and some can be used for storing data as well.
When dealing with hard drives, there are two major attachment interfaces: IDE (Integrated Device Electronics) or ATA (AT Attachment), and SCSI (Small Computer System Interface). ATA opens up the IDE interface to accept a wider variety of devices. There has been a long ongoing battle for speed and performance between IDE and SCSI, but in general, SCSI provides faster and more reliable transportation.
IEEE-1394 or FireWire provides a fast enough bus to enable hard drives to be attached to a computer by this method. There are also PCMCIA or PC Card hard drives that can be used with your computer.
The type of drives that you will be attaching to your computer will depend on the types that are supported by your motherboard or I/O cards.
Monitor
The different types of buses that can be used to provide video services include:
? ISA, which runs at a speed of 8 MHz
? PCI, which runs at a speed of 33 MHz
? AGP, which runs at a speed of 66 MHz
You have probably already guessed that the faster the bus speed, the faster your video card is likely to function. The AGP bus was designed specifically for video. In addition to a fast bus speed, video performance and color depth is provided by RAM or Video RAM. This RAM is found on the video card itself. Some high-end video cards will also have a small processor to handle some of the work of displaying information on your monitor.
Video cards traditionally allow for color depths that include:
? 4 bit or 16 colors
? 8 bit or 256 colors
? 16 bit or 65 thousand colors
? 24 bit or 16 million colors
? 32 bit or 4 billion colors
Screen resolutions usually include:
? 640 x 480
? 800 x 600
? 1024 x 768
? 1152 x 864
? 1280 x 1024
? 1600 x 1200
Modern video cards follow the SVGA (Super Video Graphics Array) standard, but support at least VGA as well. The VGA standard is output in 16 colors at 640 x 480.
Modem
Modem is short for Modulator Demodulator. Modulation refers to the conversion of a digital signal to an analog signal, and demodulation reverses this process. Your computer is digital, while the phone lines that you want to communicate over are analog. In order to allow the digital signal to be passed over the analog lines, you must use a modem.
The speeds at which modems operate have been increasing since their use with computers. They started with transfer rates of 300 bps (bits per second) and have moved up to 115 Kbps.
Today, there are more and more cases where modems have been replaced with other remote connectivity options, such as ADSL, ISDN, and Broadband Cable.
Modems may be connected to your computer through the serial port, the ISA bus, or the PCI bus. Modems may support synchronous or asynchronous communication.
Most modems that are purchased for a computer are asynchronous.
LCD and Portable Systems
Portable, or laptop, systems have a special place in the hardware technology side of computing. Portable systems make use of technologies that are not normally used by desktop or stationary computers.
In addition to standard desktop components such as hard drives, floppy drives, and CD-ROMs, you can expect to find many of the following components in use with your portable system:
? LCD (Liquid Crystal Display) panels
? PCMCIA (Personal Computer Memory Card International Association) or PC Card slot
? Battery
? Low-power CPU
? Port Replicator or Docking Station LCD panels provide a low-power, flat, thin display solution that is required by laptop systems. This technology is actually making its way into the desktop market.
There are a few standard types of LCD displays�active matrix, passive matrix, and dual scan�that differ in the way power is supplied to the diodes that make up the display and in the quality of the output.
PC Card slots offer an easy expansion slot for laptop computers. PCI and ISA slots are not suited to portable device use due to their size and lack of hot swapping.
Enter PC Card technology. The cards fit the size requirements for portable use since they are about the size of credit cards. They support hot swapping and Plug-and-Play for easy insertion and removal. Most systems come with support for Type I, II, or III cards. One of the differences in the type specification is the height of the cards. PC Cards offer a simple and expandable bus for portable device users, but may be succeeded by USB (Universal Serial Bus) devices for a number of components.
The most used PC Cards have been network cards and modems, which are often integrated onto the motherboard of most new laptops.
Since most portable devices are used remotely, batteries are another technology component that play a big role in the evelopment. Batteries come in three basic flavors:
? Nickel-Cadmium (NiCad)
? Nickel-Metal Hydride (NiMH)
? Lithium-Ion (LiIon)
Nickel-Metal Hydride batteries replaced Nickel-Cadmium batteries, since they seemed to be less susceptible to developing a charging memory. The charging memory is developed when the battery is regularly charged, and then only used a small amount before recharging. After repeating this usage pattern over several charges, the battery would only last for a short period of time. Lithium-Ion batteries are even more memory-free and do a better job of holding their charge when not in use, and their charge lasts longer when in use.
Battery life in your portable device depends on use, power management, and the battery itself.
In order to extend the battery life of your portable device as much as possible, manufacturers developed low-power versions of their CPUs. These low-power versions were then combined with motherboards that offered enhanced power management.
This allowed the speed of the processor to be reduced when not in use, further reducing power consumption.
Since the space inside a portable device is so precious, port replicators and docking stations were created, which allows for a minimum of resources built into the unit. For example, you can purchase an ultra-light portable computer that comes with only one external port, a CD-ROM, and no floppy drive. Such a computer is great when you want to carry it around, but lousy when it comes to getting data in and out of the unit. Enter the port replicator or docking station that connects to the one external (usually proprietary) connector on the back of the unit. The port replicator is usually a smaller unit than the docking station, and usually only provides additional ports such as video, serial, parallel, and additional PCMCIA slots; however, it could also provide networking, floppy disk, and additional battery. The docking station is a larger unit that can provide additional hard drives, PCI and ISA slots, and other components that would normally be included in desktop computer.
Boot Process
The boot process begins with the application of electricity to your computer, which starts the POST (Power On Self Test) and moves through a procedure that locates a bootable device and loads an operating system.
The POST starts the procedure and performs the following tasks:
? Testing RAM
? Locating devices, such as hard drives and floppy drives
? Searching drives for bootable devices
? Loading the boot sector from a bootable device
? Transferring control of computer to operating system
Bootable devices are scanned for in the order of preference that is specified in the computer�s CMOS�usually the A: drive, C: drive, CD-ROM, and network. For each device, the boot sector is examined for a program to load an OS. For hard drives, the boot sector will be on the partition that is marked as active.
The program that is searched for in the boot sector is the boot loader�io.sys on Windows 9x computers and ntldr on Windows NT and Windows 2000 computers.
The boot loader takes control of the computer from the POST process. It is also responsible for locating the files that make up the rest of the OS and loading them, or reporting the errors.
Ports
Sailing ports provide a location for ships to load and unload goods that are being transferred from one location to another. On your computer, ports act as connection points for cables, enabling the transfer of data between your computer and another device. There are several different types of connectors and cables that are used to join devices together. The list of devices that can be communicated with through the different types of ports is limitless. Some of the basic types of ports and their uses are listed in the Table.
| Serial | Connects serial devices, such as modems, to your computer. |
| Parallel | Connects parallel devices, such as printers, to your computer. |
| Video | Connects a monitor to your computer. |
| USB | Connects various types of devices to your computer. This port is being used to connect new versions of devices that would have used other ports in the past. Devices that use this port include: printers, modems, mice, keyboards, and scanners. |
| Keyboard | Connects a keyboard to your computer. |
| Mouse | Connects a mouse to your computer. |
PDA
It was less than twenty years ago when standard computers came with 4K of memory and you loaded programs from audiotape. Ten years ago, you were able to buy a Sharp Electronic Organizer with 256K of memory. The Sharp device was about the size of a bundle of dollar bills (when closed) with a small qwerty keyboard and an eight-line by forty-character display. These devices were capable of storing schedules, addresses, and a small database. I used to keep our corporate price list in mine. At the time, I thought that this device was absolutely amazing.
Current versions of the Palm PDA from Palm Inc. are about half the size of a CD-ROM jewel case. They sport a 65,000 color display, 8MB of RAM, and a proprietary expansion card slot that allows you to add storage space and applications to your Palm PDA.
Current versions of Pocket PC PDAs�such as the Compaq iPAQ�come with a scaled-back version of Microsoft office (Word and Excel), Internet Explorer, and Microsoft Reader (which supports a new electronic book format). This PDA includes a 206 MHz Intel processor, 64MB of RAM and 16MB of Flash ROM memory.
The screen on the PDA supports 4,096 colors, and it supports a PC card (PCMCIA card) and CF card (Compact Flash, which is a storage medium) expansion.
These new PDAs are capable of functioning as mini-extensions of your desktop computer.
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Filed Under: Computer Hardware
