Technical Questions Answers » Computing

What is PCI?

admin — Sat, 25 Jul 2009 15:52:56 +0000

PCI (Peripheral Component Interconnect) is a computer bus used for attaching peripheral devices to a computer motherboard. It is the most popular local I/O bus used in today. PCI provides a shared data path between the CPU and peripheral controllers in every computer models, from laptops to mainframes. Developed by the Intel Corporation, PCI first appeared in computers in 1993 and co-existed with the ISA bus for several years. It soon displaced the ISA and VESA local bus and became the standard expansion bus used in PCs. Today, most computers have only PCI slots and one AGP slot for a display adapter.

PCI supports both 32-bit and 64-bit data paths and can run at clock speeds of 33MHz or 66MHz. When implemented at 32 bits and 33 MHz, PCI yields a throughput rate of 133 MBps. PCI also has the ability to support bus mastering. The PCI specification covers the physical size of the bus, including wire spacing, bus timing, electrical characteristics, and protocols. The specification can be purchased from the PCISIG also known as the PCI Special Interest Group.

PCI Configuration
PCI devices are plug and play devices, meaning they load automatically when you connect them. Generally, the system firmware inspects each device's PCI Configuration Space and distributes resources accordingly. A device can request up to six areas of I/O port space or memory space. Each device can also have an additional ROM which can include executable x86 or PA-RISC code, an EFI driver, or an Open Firmware.

While configuring PCI, interrupts are usually allocated to the device by firmware rather than using jumpers on the card. System software tries to assign specific interrupts to each device to boost their performance. Most PCI devices require special hardware to support sharing an interrupt port because it needs a method to inform if an interrupt is for itself or for a specific device sharing the IO port.

History of PCI
Intel Corporation started the work on Peripheral Component Interconnect or PCI in 1990. On June 22 1992, PCI 1.0 was introduced in the computer world. PCI 1.0 was just a component-level specification. PCI 2.0, released in the next year, was the first to establish standards for the connector and motherboard slot. PCI was implemented in servers and eventually it replaced the MCA and EISA and became the server expansion bus of choice.

However, PCI took some time to supercede VESA Local Bus, commonly known as VLB; it also took some time to become the basic I/O bus standard in second-generation Pentium computers. By 1996 VESA Local Bus become extinct and PCI was adopted by almost all manufactures, even in 486 computers. But EISA survived a bit longer, until 2000. PCI was also adopted by Apple Computer for their professional Power Macintosh computers in mid 1995. The consumer Performa product line also adopted PCI in mid-1996, replacing LC PDS.

PCI added several new features and performance improvements in its latest versions. This includes a 66 MHz 3.3 V standard and 133 MHz PCI-X. Another improvement is the adaptation of PCI signaling to other form factors. The serial PCI Express standard, introduced in 2004, is the latest release in the computer market and has been well received.

PCI Express
PCI Express, formerly 3GIO/Arapaho, is a brand new interface developed using PCI programming concepts. PCI Express features a serial physical-layer protocol and various connectors. PCI Express is expected to replace the PCI and PCI derived AGP buses in the future.

What is Tablet PC?

admin — Sat, 25 Jul 2009 15:47:41 +0000

Tablet computers are self contained pen-driven computers generally for specific purposes, environments and user needs and include a liquid crystal display screen (LCD) positioned in sealing engagement behind an aperture formed into the front housing of the housing assembly. A tablet computer has a flat, plane box shaped main body, and does not have keyboards as standard equipment, and has a tablet that also serves as displays provided on their fronts. Selected conventional electronics are positioned within the interior volume of the housing assembly with output connectors as required disposed through the central wall of the rear housing.

The tablet PC may have a touch display panel and may be able to connect to another PC through a cabled or a wireless means. Among other ways of entering textual information, Tablet PC users will often use a stylus, also referred to herein as a pen, to write on a display area of the Tablet PC. Such a pen or stylus may also be used as a pointing device directly on the screen or above the screen to make various in-air gestures. To operate the tablet PC, which is similar to common writing types, a special pen is used with a touch display screen to perform various operating procedures. The pen-based input devices fall into two broad categories defined by the type of tablet input device employed. The first type of tablet input device is a transparent overlay that sits on top of the graphics display so that the graphics display image is viewable through the tablet. The active area of the tablet input device correspondingly maps to the graphics display area. The second type of tablet input device is a digitizing table with an opaque tablet that sits off to the side of the graphics display. Similarly to the transparent overlay tablet input device, the active area of the tablet corresponds to the graphics display area. Graphical user interfaces or GUIs are becoming increasingly popular with computer users. Many people find that computers having GUIs are easier to learn and use than comparable computers without GUIs. Typically, graphical images can be input into the pen computer systems by merely moving the stylus across the surface of the screen, i.e. making a “stroke” on the screen. The pen input operation may be performed on a desk, or by holding the pen in one hand and supporting the computer with the other hand.

Tablet PCs are likely to become increasingly popular for a variety of reasons. Compared to a conventional laptop computer, a tablet PC is more compact in size and is more portable, since the LCD monitor and the system main board of the tablet PC are integrated together. The tablet PC changes the input habits of the computer user and advances the information industry to a new milestone. For instance, in the context of taking notes during a meeting, a Tablet PC presents less of a barrier between individuals than does a laptop computer. In addition, Tablet PC's allow for capturing of handwritten notes so that Tablet PC users are able to take notes in their own handwriting, in an unobtrusive manner similar to taking handwritten notes with a pen and paper. Tablet PCs provide a very natural way to interact with a computer, namely, by writing on it, without sacrificing the power or utility of various operating systems and/or various operating system-based desktop applications. Tablet personal computers are not limited to computers running a “Windows” operating system. Instead, a tablet PC, may run any other known, or later-developed, operating system. Because new operating systems are available that are specifically designed for this application, tablets can support all existing applications without modification, making it as powerful as it is portable. While providing the simplicity of pen and paper, tablet PC's have the potential to provide many features and benefits provided by word processors and other personal computer software, including sharing of notes among meeting participants in real-time during a meeting via a wireless communication link. The tablet PC, which combines the functions of a wireless web with a notebook computer, fills an important need in the processing of information. Due to the growing popularity of personal digital assistants and tablet computers, notebook computers are now being configured to alternatively operate as a tablet computer, with a stylus operating as the input device.

What are Wireless Keyboards?

admin — Sat, 25 Jul 2009 15:44:59 +0000

A keyboard is the part of a computer system that enables the user to control certain aspects of the computer. It allows a user to enter data, compose written verbiage and do other useful tasks. When a user depresses a key on a keyboard, a change in the current flowing through the circuit associated with that key occurs. In the keyboard, a number of key switches corresponding to the keys are arranged in matrix on the intersections of drive lines and receive lines. The keyboard includes one or more keys with symbols such as the letters A to Z and numbers and punctuation marks. A keyboard may also typically includes additional keys of various sizes such as a space bar, an enter key and the like. The keyboard is provided with a microcontroller which performs predetermined processing in response to key press and key release operations. Depending on which key circuit carries the signal to the microcontroller, the microcontroller generates a number, called a scan code. Each key has a unique scan code. The microcontroller detects the change in current from a depressed key. To distinguish between a current change that results from a depressed key and an aberrant current fluctuation that results from key bounce, the microcontroller scans the key switch matrix hundreds of times each second. Only current changes that last for two or more scans are acted upon by the microcontroller.
Keyboards typically come in two basic configurations: wired and wireless. Most keyboards are connected to the computer by a length of electrical cable, and are designed to be used in a fixed horizontal manner as with a conventional typewriter. As the PC has become more popular in general households, there has been a problem that the cable is obstructive or too short for satisfactory use. The computer user is severely restricted in terms of physical location and movement, and is typically required to be a foot or two in front of the computer monitor screen. Another disadvantage of the standard keyboard is that it consumes otherwise usable space, such as area on a desktop. The fixed type of keyboard cannot as easily be used in the standing position if it had been previously adjusted for use while sitting, and the keyboard is impractical were the user to assume a reclining position because the keyboard requires a stable horizontal platform for mechanical stability. While such keyboards are generally connected to PC main bodies via cables, various peripherals including keyboards and pointing devices such as mice are also connected to the PC main bodies, so that cables for connecting them are often complicated, causing troubles for deskwork frequently. While wired keyboards are generally less expensive, wireless keyboards are becoming more popular because they eliminate the need for cords that otherwise clutter up the workspace. Thus, both types of keyboards are found in a variety of settings, depending on what is needed.
In order to solve the problems that occur because of keyboard device and/or mouse device being wired to computer main body, many keyboards have evolved from wired and limited range operations to wireless and remote operations. Wireless keyboards have a number of advantages over the more common wire connected keyboards employed in computer systems. Wireless keyboards enable computer users to input data from positions spaced from the remainder of a processor-based system. This gives the user the additional freedom to make data entries without requiring the user to sit proximate to the processor-based system. Wireless keyboards offer more flexibility to the user to position him or her self relative to the computer. This can reduce strain and tiredness associated with computer use. Wireless keyboards reduce the amount of wires connected over or around a desktop and reduce clutter and complicated wiring tangles. As more add on peripherals are included in typical computer systems to support more advanced performance, the removal of cable wiring for a keyboard is of particular importance in saving space around the computer body. This creates a cleaner look to the overall system and can give the computer system a more sophisticated and/or expensive look. With the wireless keyboard, the installation and operation become simple because wiring cable is not needed for data transmission to computer, and numbers of users are able to use a computer simultaneously by connecting numerous keyboards to a computer. On consideration of convenience, wireless keyboard are popularly used with various computing apparatuses, e.g., desk-top computers, notebook computers, personal digital assistants, mobile phones, and pocket computers.
The wireless keyboards currently available are either infrared based or RF based transmission systems. Wireless keyboard transmits data to the central processing unit (CPU) of the computer via either radio frequency (RF) signals or infrared (IR) signals. In a wireless keyboard, a microcontroller scans the key matrix to detect which keys are pressed, and transmits key data corresponding to the pressed keys via infrared or radio waves. Each time the keyboard sends a wireless key make code to the host computer indicating that a key has been depressed, the host computer awaits a key break code indicating that the key has been released. If the key make code is not followed within a predetermined time frame by the break code, the operating system automatically repeats the key represented by the make code. The delay between the make code and automatic repeat is user configurable. The wireless keyboard contains an infrared or radio frequency transmitter, and typically a small receiving unit is located in the vicinity of the computer and connected to it by electrical cable. Current wireless keyboards employ the same transmission formats, or schemes, used with hardwired keyboards. Typically, each of the keys of a keyboard are treated as a position in a matrix. The index of the matrix position of a particular key character is transmitted to the computer via pulses of light. An infrared wireless keyboard simply uses an infrared transmitter in the keyboard and an infrared receiver in a computing apparatuses to establish a link between the keyboard and the computing apparatus. Radio frequency (RF) wireless keyboards use RF antennas for transmitting RF signals. For a wireless keyboard, battery capacity is a critical design parameter. By reducing the power consumed when transmitting key characters to the computer, the battery can be advantageously made smaller while maintaining battery life between recharging. Another advantage of reduced power consumption is longer battery life.
The use of wireless IR communications has been known for quite some time. A typical application for such IR communications has been, and is currently, for remote control of electronic devices such as television sets, video cassette recorders, home audio systems, etc. In a wireless IR keyboard, each time a keyboard key is pressed a digital code corresponding to the pressed key is generated, modulated onto an IR carrier, and transmitted to the special set top box. The set top box receives the IR signal, decodes the signal and determines which key was pressed. An infrared wireless keyboard system allows multiple users to operate wireless keyboards without interference. Infrared wireless keyboard systems can accommodate multiple users with multiple channels. Each channel is programmed with an individual identifier code and an individual carrier frequency. When a key is depressed, the key code and ID code are transmitted according to the known RS-232 format at a designated frequency. The carrier frequency is designated by the user, and is selected from a range of frequencies. The receiver, which is coupled to the computer system, can determine from the received ID code which channel the keyboard is using. The infrared wireless keyboard typically operates on a six-volt power source that is commonly derived from four 1.5-volt batteries. The infrared systems are the simplest and least expensive, however, they require a line of sight to the receiver. This can result in inconsistent transmission as the keyboard is moved or if other objects block the transmission path. RF systems do not suffer from this problem but are more expensive than infrared systems. The reliability of transmission in RF systems at a given range depends on the RF frequency and the power and quality of the transmitter.
While wireless keyboards are becoming acceptable substitutes for cable keyboards, there are still problems associated with wireless transmission. The primary reason that wireless keyboards have not displaced wire connected keyboards to a greater extent is the need for replacing batteries. When batteries fail in a wireless keyboard computer system the system is useless until the batteries are replaced. In some occasions, an input from a wireless keyboard to an information processing device is hindered by communication incapability depending on a relation between positions of the information processing device and the wireless keyboard. The wireless keyboard may have a relatively limited effective range. If the keyboard is moved too far away from the host processor-based system, the link may be lost. Similarly, if severe interference is encountered, the link may be lost as well. The infrared wireless keyboard has large power consumption requirements because of the infrared transmitter. The increased power consumption reduces overall battery life so that the batteries must be replaced more often. Radio frequency (RF) wireless keyboards addressed some of the shortcomings of the infrared wireless keyboards. However, the production costs associated with the RF wireless keyboard are high because complex antenna circuitry is used. Moreover, in some instances even the complex and expensive antenna circuitry still lacks the efficiency for transmitting RF signals.

What is Power supply?

admin — Tue, 08 Jul 2008 16:28:28 +0000

A Power supply also known as power supply unit or PSU, is the component that supplies power to an electronic device such as a computer. All electronic circuits need to be powered from a reliable direct current (DC) source and such power source must be generated from an everlasting source of alternating current (AC) power.

There are a wide variety of power supplies including batteries, fuel cells, electro-mechanical generators, alternating current to direct current supplies, inverters, and alternating current supplies, among many others.

Batteries are a type of electrochemical cell containing a pair of electrodes and an electrolyte disposed between the electrodes. Batteries can be grouped into a primary type and a secondary type. The primary type comprises disposable batteries, and the secondary type comprises rechargeable batteries. The rechargeable batteries can further be grouped into four types: NiMH (nickel metal hydride), NiCd (nickel cadmium), Li-Ion (Lithium Ion), and sealed lead acid batteries. Rechargeable batteries have gained wide acceptance and usage as power sources for portable appliances. Mobile phones, digital cameras, camcorders, laptop computers, and personal digital assistants are just a few of the many appliances now using rechargeable battery technology. Battery chargers are often provided as either internal or external devices to be used to recharge these batteries. Generally, the rechargeable battery is charged with a transformer that converts current from a conventional electrical outlet or automobile lighter into direct current suitable for charging the battery. Rechargeable batteries are provided with a variety of protective functions for preventing damage to the battery caused by abnormal use such as overcharging, overdischarging, short-circuiting between the positive and negative electrodes. An uninterruptible power supply (UPS) is a type of power supply used to power and protect an electrical load that is sensitive to fluctuations in or the absence of electrical power. A UPS typically comprises a rectifier, inverter, and battery charger.

Most personal computers can be plugged into standard electrical outlets. The power supply then pulls the required amount of electricity and converts the AC current to DC current. It also regulates the voltage to eliminate spikes and surges common in most electrical systems. Not all power supplies, however, do an adequate voltage-regulation job, so a computer is always susceptible to large voltage fluctuations.

Is a BIOS Upgrade Available?

admin — Sat, 23 Feb 2008 18:55:55 +0000

Most of the time the BIOS have an upgrade available, to know if you have BIOS upgrade you need to visit the pc maker site. Most computer makers such as IBM, Dell, Compaq and Packard Bell have these updates on their web sites.

After you find the manufacturer that provided the BIOS code, the next step is to determine whether the BIOS can be upgraded. Unless you are very certain that your BIOS needs to be updated, check with your hardware manufacturer. If you improperly flash (update) your BIOS, you may be unable to start your computer, and this may result in data loss or other problems.