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computer
Internet History
This Internet Timeline begins in 1962, before the word ‘Internet’ is invented. The world’s 10,000 computers are primitive, although they cost hundreds of thousands of dollars. They have only a few thousand words of magnetic core memory, and programming them is far from easy.Domestically, data communication over the phone lines is an AT&T monopoly. The ‘Picturephone’ of 1939, shown again at the New York World’s Fair in 1964, is still AT&T’s answer to the future of worldwide communications. But the four-year old Advanced Research Projects Agency (ARPA) of the U.S. Department of Defense, a future-oriented funder of ‘high-risk, high-gain’ research, lays the groundwork for what becomes the ARPANET and, much later, the Internet.By 1992, when this timeline ends,the Internet has one million hosts .
computer-memory-pyramid
system properties
virtual memory
Sunday, June 22, 2008
Inside the PC
Data Structure and Algorithms
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Data Structure and Algorithms
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Networking
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Friday, May 30, 2008
Components of video card.
Components
A video card consists of a printed circuit board on which the components are mounted. These include:
Graphics processing unit (GPU)
Main article: Graphics processing unit
A GPU is a dedicated graphics microprocessor optimized for floating point calculations which are fundamental to 3D graphics rendering. The main attributes of the GPU are the core clock rate, which typically ranges from 250 MHz to 850 MHz, and the number of pipelines (vertex and fragment shaders), which translate a 3D image characterized by vertices and lines into a 2D image formed by pixels.
Video BIOS
The video BIOS or firmware contains the basic program that governs the video card's operations and provides the instructions that allow the computer and software to interface with the card. It may contain information on the memory timing, operating speeds and voltages of the graphics processor and RAM and other information. It is sometimes possible to change the BIOS (e.g., to enable factory-locked settings for higher performance) although this is typically only done by video card overclockers, and has the potential to irreversibly damage the card.
Video memory
If the video card is integrated in the motherboard, it may use the computer RAM memory (lower throughput). If it is not integrated, the video card will have its own video memory, called Video RAM. The memory capacity of most modern video cards range from 128 MB to 2.0 GB[8]. Since video memory needs to be accessed by the GPU and the display circuitry, it often uses special high speed or multi-port memory, such as VRAM, WRAM, SGRAM, etc. Around 2003, the video memory was typically based on DDR technology. During and after that year, manufacturers moved towards DDR2, GDDR3 and GDDR4. The memory clock rate in modern cards are generally between 400 MHz and 2.4 GHz.
Video memory may be used for storing other data as well as the screen image, such as the Z-buffer, which manages the depth coordinates in 3D graphics.
RAMDAC
Random Access Memory Digital-to-Analog Converter. RAMDAC takes responsibility for turning the digital signals produced by the computer processor into an analog signal which can be understood by the computer display. Depending on the number of bits used and the RAMDAC data transfer rate, the converter will be able to support different computer display refresh rates. With CRT displays, it is best to work over 75 Hz and never under 60 Hz, in order to minimise flicker.[9] (With LCD displays, flicker is not a problem.) Due to the growing popularity of digital computer displays and the migration of some of its functions to the motherboard, the RAMDAC is slowly disappearing. All current LCD and plasma displays and TVs work in the digital domain and do not require a RAMDAC. There are few remaining legacy LCD and plasma displays which feature analog inputs (VGA, component, SCART etc.) only; these do require a RAMDAC but they reconvert the analog signal back to digital before they can display it, with the unavoidable loss of quality stemming from this digital-to-analog-to-digital conversion.
A video card consists of a printed circuit board on which the components are mounted. These include:
Graphics processing unit (GPU)
Main article: Graphics processing unit
A GPU is a dedicated graphics microprocessor optimized for floating point calculations which are fundamental to 3D graphics rendering. The main attributes of the GPU are the core clock rate, which typically ranges from 250 MHz to 850 MHz, and the number of pipelines (vertex and fragment shaders), which translate a 3D image characterized by vertices and lines into a 2D image formed by pixels.
Video BIOS
The video BIOS or firmware contains the basic program that governs the video card's operations and provides the instructions that allow the computer and software to interface with the card. It may contain information on the memory timing, operating speeds and voltages of the graphics processor and RAM and other information. It is sometimes possible to change the BIOS (e.g., to enable factory-locked settings for higher performance) although this is typically only done by video card overclockers, and has the potential to irreversibly damage the card.
Video memory
If the video card is integrated in the motherboard, it may use the computer RAM memory (lower throughput). If it is not integrated, the video card will have its own video memory, called Video RAM. The memory capacity of most modern video cards range from 128 MB to 2.0 GB[8]. Since video memory needs to be accessed by the GPU and the display circuitry, it often uses special high speed or multi-port memory, such as VRAM, WRAM, SGRAM, etc. Around 2003, the video memory was typically based on DDR technology. During and after that year, manufacturers moved towards DDR2, GDDR3 and GDDR4. The memory clock rate in modern cards are generally between 400 MHz and 2.4 GHz.
Video memory may be used for storing other data as well as the screen image, such as the Z-buffer, which manages the depth coordinates in 3D graphics.
RAMDAC
Random Access Memory Digital-to-Analog Converter. RAMDAC takes responsibility for turning the digital signals produced by the computer processor into an analog signal which can be understood by the computer display. Depending on the number of bits used and the RAMDAC data transfer rate, the converter will be able to support different computer display refresh rates. With CRT displays, it is best to work over 75 Hz and never under 60 Hz, in order to minimise flicker.[9] (With LCD displays, flicker is not a problem.) Due to the growing popularity of digital computer displays and the migration of some of its functions to the motherboard, the RAMDAC is slowly disappearing. All current LCD and plasma displays and TVs work in the digital domain and do not require a RAMDAC. There are few remaining legacy LCD and plasma displays which feature analog inputs (VGA, component, SCART etc.) only; these do require a RAMDAC but they reconvert the analog signal back to digital before they can display it, with the unavoidable loss of quality stemming from this digital-to-analog-to-digital conversion.
Outputs
The most common connection systems between the video card and the computer display are:
HD-15
Analog-based standard adopted in the late 1980s designed for CRT displays, also called VGA connector. Some problems of this standard are electrical noise, image distortion and sampling error evaluating pixels.
DVI
Digital-based standard designed for displays such as flat-panel displays (LCDs, plasma screens, wide High-definition television displays) and video projectors. It avoids image distortion and electrical noise, corresponding each pixel from the computer to a display pixel, using its native resolution.
Video In Video Out (VIVO) for S-Video, Composite video and Component video
Included to allow the connection with televisions, DVD players, video recorders and video game consoles. They often come in two 9-pin Mini-DIN connector variations, and the VIVO splitter cable generally comes with either 4 connectors (S-Video in and out + composite video in and out) or 6 connectors (S-Video in and out + component PB out + component PR out + component Y out (also composite out) + composite in).
The most common connection systems between the video card and the computer display are:
HD-15
Analog-based standard adopted in the late 1980s designed for CRT displays, also called VGA connector. Some problems of this standard are electrical noise, image distortion and sampling error evaluating pixels.
DVI
Digital-based standard designed for displays such as flat-panel displays (LCDs, plasma screens, wide High-definition television displays) and video projectors. It avoids image distortion and electrical noise, corresponding each pixel from the computer to a display pixel, using its native resolution.
Video In Video Out (VIVO) for S-Video, Composite video and Component video
Included to allow the connection with televisions, DVD players, video recorders and video game consoles. They often come in two 9-pin Mini-DIN connector variations, and the VIVO splitter cable generally comes with either 4 connectors (S-Video in and out + composite video in and out) or 6 connectors (S-Video in and out + component PB out + component PR out + component Y out (also composite out) + composite in).
Other Types of Connection Systems
Composite video
Analog system, with lower resolution. It uses RCA connector.
Component video
It has three cables, each with RCA connector (YCBCR); it is used in projectors, DVD players and some televisions.
DB13W3
an analogue standard once used by Sun Microsystems, SGI and IBM.
HDMI
digital technology released in 2003, whose goal is to replace all the others.
DisplayPort
An advanced license and royalty-free digital audio/video interconnect released in 2007.Cooling devices
Video cards may use a lot of electricity, which is converted into heat. If the heat isn't dissipated, the video card could overheat and be damaged. Cooling devices are incorporated to transfer the heat elsewhere. Three types of cooling devices are commonly used on video cards:
Heat sink: generally referred to as a passive cooling device, it has no moving parts and, therefore, is soundless and very reliable; it conducts heat from the GPU to some cooling medium, such as air, using thermal contact. Its effectiveness depends on its size, contact area, material (generally copper or aluminium) and other characteristics including shape. To increase effectiveness, this is typically (but not necessarily) combined with a computer fan.
Computer fan: an example of an active cooling device, a small electrical fan which drives air across a heat sink. It is more effective than a heat sink alone at cooling, but due to the moving parts a fan requires maintenance and possible replacement. It also generates noise.
Water block: a heat sink which transfers heat from the GPU to a circulating liquid, rather than the air. This liquid is carried outside the computer case and the heat dissipated to the air by a heat sink (with or without a fan). Typically part of a larger liquid cooling system for the computer as a whole, this approach has the advantages outlined in that article (to summarise, the heat sink design and positioning is not restricted by being located inside a computer case).
Power demand
As the processing power of video cards has increased, so has their demand for electrical power. Present fast video cards tend to consume a great deal of power. While CPU and power supply makers have recently moved toward higher efficiency, power demands of GPUs have continued to rise, so the video card may be the biggest electricity user in a computer.[11] Although power supplies are increasing their power too, the bottleneck is due to the PCI-Express connection, which is limited to supplying 150 W.[12] Nowadays, video cards with a power consumption over 150 W usually include a six-pin or eight-pin power socket that connects directly to the power supply,[13] avoiding motherboard connection and the PCIe port.
Composite video
Analog system, with lower resolution. It uses RCA connector.
Component video
It has three cables, each with RCA connector (YCBCR); it is used in projectors, DVD players and some televisions.
DB13W3
an analogue standard once used by Sun Microsystems, SGI and IBM.
HDMI
digital technology released in 2003, whose goal is to replace all the others.
DisplayPort
An advanced license and royalty-free digital audio/video interconnect released in 2007.Cooling devices
Video cards may use a lot of electricity, which is converted into heat. If the heat isn't dissipated, the video card could overheat and be damaged. Cooling devices are incorporated to transfer the heat elsewhere. Three types of cooling devices are commonly used on video cards:
Heat sink: generally referred to as a passive cooling device, it has no moving parts and, therefore, is soundless and very reliable; it conducts heat from the GPU to some cooling medium, such as air, using thermal contact. Its effectiveness depends on its size, contact area, material (generally copper or aluminium) and other characteristics including shape. To increase effectiveness, this is typically (but not necessarily) combined with a computer fan.
Computer fan: an example of an active cooling device, a small electrical fan which drives air across a heat sink. It is more effective than a heat sink alone at cooling, but due to the moving parts a fan requires maintenance and possible replacement. It also generates noise.
Water block: a heat sink which transfers heat from the GPU to a circulating liquid, rather than the air. This liquid is carried outside the computer case and the heat dissipated to the air by a heat sink (with or without a fan). Typically part of a larger liquid cooling system for the computer as a whole, this approach has the advantages outlined in that article (to summarise, the heat sink design and positioning is not restricted by being located inside a computer case).
Power demand
As the processing power of video cards has increased, so has their demand for electrical power. Present fast video cards tend to consume a great deal of power. While CPU and power supply makers have recently moved toward higher efficiency, power demands of GPUs have continued to rise, so the video card may be the biggest electricity user in a computer.[11] Although power supplies are increasing their power too, the bottleneck is due to the PCI-Express connection, which is limited to supplying 150 W.[12] Nowadays, video cards with a power consumption over 150 W usually include a six-pin or eight-pin power socket that connects directly to the power supply,[13] avoiding motherboard connection and the PCIe port.
How Video card work in computer.
Video card
A video card, also referred to as a graphics accelerator card, display adapter, graphics card, and numerous other terms, is an item of personal computer hardware whose function is to generate and output images to a display. It operates on similar principles as a sound card or other peripheral devices.
The term is usually used to refer to a separate, dedicated expansion card that is plugged into a slot on the computer's motherboard, as opposed to a graphics controller integrated into the motherboard chipset. An integrated graphics controller may be referred to as an "integrated graphics processor" (IGP).
Some video cards offer added functions, such as video capture, TV tuner adapter, MPEG-2 and MPEG-4 decoding or even FireWire, mouse, light pen, joystick connectors, or even the ability to connect multiple monitors.
Video cards are not used exclusively in IBM type PCs; they have been used in devices such as Commodore Amiga (connected by the slots Zorro II and Zorro III), Apple II, Apple Macintosh, Atari Mega ST/TT (attached to the MegaBus or VME interface), Spectravideo SVI-328, MSX and in video game consoles.
what is CD-ROM drives ?
CD-ROM drivesCD-ROM discs are read using CD-ROM drives, which are now almost universal on personal computers. A CD-ROM drive may be connected to the computer via an IDE (ATA), SCSI, S-ATA, Firewire, or USB interface or a proprietary interface, such as the Panasonic CD interface. Virtually all modern CD-ROM drives can also play audio CDs as well as Video CDs and other data standards when used in conjunction with the right software.
Laser and Optics
CD-ROM drives employ a near-infrared 780 nm laser diode. The laser beam is directed onto the disc via an opto-electronic tracking module, which then detects whether the beam has been reflected or scattered.
Transfer rates
The rate at which CD-ROM drives can transfer data from the disc is gauged by a speed factor relative to music CDs: 1x or 1-speed which gives a data transfer rate of 150 kilobytes per second in the most common data format. By increasing the speed at which the disc is spun, data can be transferred at greater rates. For example, a CD-ROM drive that can read at 8x speed spins the disc at up to 4000 rpm (compared to the 500 rpm maximum for 1x speed), giving a transfer rate of 1.2 megabytes per second. Above 12x speed, vibration and heat can become a problem. CD-ROM drives above this speed tackle the problem in several ways. Constant angular velocity (CAV) drives spin the disc at a constant rate, leading to faster data transfer when reading from the outer parts of the disc, but slower towards the centre. 20x was thought to be the maximum speed due to mechanical constraints until Samsung Electronics introduced the SCR-3230, a 32x CD-ROM drive which uses a ball bearing system to balance the spinning disc in the drive to reduce vibration and noise. As of 2004, the fastest transfer rate commonly available is about 52x or 10,350 rpm and 7.62 megabytes per second, though this is only when reading information from the outer parts of a disc. Future speed increases based simply upon spinning the disc faster are particularly limited by the strength of polycarbonate plastic used in CD manufacturing, though improvements can still be obtained by the use of multiple laser pickups as demonstrated by the Kenwood TrueX 72x which uses seven laser beams and a rotation speed of approximately 10x.
CD-Recordable drives are often sold with three different speed ratings, one speed for write-once operations, one for re-write operations, and one for read-only operations. The speeds are typically listed in that order; ie a 12x/10x/32x CD drive can, CPU and media permitting, write to CD-R discs at 12x speed (1.76 MB/s), write to CD-RW discs at 10x speed (1.46 MB/s), and read from CD discs at 32x speed (4.69 MB/s).
The 1x speed rating for CDs (150 kB/s) is not to be confused with the 1x speed rating for DVDs (1.32 MB/s).
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