Saturday, December 1, 2007

RAM & ROM


What is RAM?
RAM stands for Random Access Memory. RAM provides space for your computer to read and write data to be accessed by the CPU (central processing unit). When people refer to a computer's memory, they usually mean its RAM.
New computers typically come with at least 256 megabytes (MB) of RAM installed, and can be upgraded to 512MB or even a gigabyte or more.
If you add more RAM to your computer, you reduce the number of times your CPU must read data from your hard disk. This usually allows your computer to work considerably faster, as RAM is many times faster than a hard disk.
RAM is volatile, so data stored in RAM stays there only as long as your computer is running. As soon as you turn the computer off, the data stored in RAM disappears.
When you turn your computer on again, your computer's boot firmware (called BIOS on a PC) uses instructions stored semi-permanently in ROM chips to read your operating system and related files from the disk and load them back into RAM.
Note: On a PC, different parts of RAM may be more or less easily accessible to programs. For example, cache RAM is made up of very high-speed RAM chips which sit between the CPU and main RAM, storing (i.e., caching) memory accesses by the CPU. Cache RAM helps to alleviate the gap between the speed of a CPU's megahertz rating and the ability of RAM to respond and deliver data. It reduces how often the CPU must wait for data from main memory.
RAM Defined
RAM (random access memory) is the place in a computer where the operating system, application programs, and data in current use are kept so that they can be quickly reached by the computer's processor. RAM is much faster to read from and write to than the other kinds of storage in a computer, the hard disk, floppy disk, and CD-ROM. However, the data in RAM stays there only as long as your computer is running. When you turn the computer off, RAM loses its data. When you turn your computer on again, your operating system and other files are once again loaded into RAM, usually from your hard disk.
RAM can be compared to a person's short-term memory and the hard disk to the long-term memory. The short-term memory focuses on work at hand, but can only keep so many facts in view at one time. If short-term memory fills up, your brain sometimes is able to refresh it from facts stored in long-term memory. A computer also works this way. If RAM fills up, the processor needs to continually go to the hard disk to overlay old data in RAM with new, slowing down the computer's operation. Unlike the hard disk which can become completely full of data so that it won't accept any more, RAM never runs out of memory. It keeps operating, but much more slowly than you may want it to.
How Big is RAM?
RAM is small, both in physical size (it's stored in microchip modules) and in the amount of data it can hold. It's much smaller than your hard disk. A typical computer may come with 32 million bytes of RAM and a hard disk that can hold 4 billion bytes. RAM comes in the form of "discrete" (meaning separate) microchip modules that plug into holes in the computer's motherboard. These holes connect through a bus or set of electrical paths to the processor. The hard drive, on the other hand, stores data on a magnetized surface that looks like a phonograph record.
Today's personal computers come with 16 or more megabytes of RAM, usually increasing in multiples of 8 megabytes. Users of graphic applications usually need 32, 64, or 128 or even more megabytes of memory. Most personal computers are designed to allow you to add additional RAM modules up to a certain limit (for example, up to 64 or 128 megabytes). Having more RAM in your computer reduces the number of times that the computer processor has to read data in from your hard disk, an operation that takes much longer than reading data from RAM. (RAM access time is expressed in nanoseconds; hard disk access time is expressed in milliseconds.)
Why Random Access
RAM is called "random access" because any storage location can be accessed directly. Originally, the term distinguished regular core memory from offline memory, usually on magnetic tape in which an item of data could only be accessed by starting from the beginning of the tape and finding an address sequentially. Perhaps it should have been called "nonsequential memory" because RAM access is hardly random. RAM is organized and controlled in a way that enables data to be stored and retrieved directly to specific locations. A term IBM has preferred is direct access storage or memory. Note that other forms of storage such as the hard disk and CD-ROM are also accessed directly (or "randomly") but the term random access is not applied to these forms of storage.
In addition to disk, floppy disk, and CD-ROM storage, another important form of storage is read-only memory (ROM), a more expensive kind of memory that retains data even when the computer is turned off. Every computer comes with a small amount of ROM that holds just enough programming so that the operating system can be loaded into RAM each time the computer is turned on.
Briefly How RAM Works
What RAM Looks Like
In general, RAM is much like an arrangement of post-office boxes in which each box can hold a 0 or a 1. Each box has a unique address that can be found by counting across columns and then counting down by row. In RAM, this set of post-office boxes is known as an array and each box is a cell. To find the contents of a box (cell), the RAM controller sends the column/row address down a very thin electrical line etched into the chip. There is an address line for each row and each column in the set of boxes. If data is being read, the bits that are read flow back on a separate data line. In describing a RAM chip or module, a notation such as 256Kx16 means 256 thousand columns of cells standing 16 rows deep.
In the most common form of RAM, dynamic RAM, each cell has a charge or lack of charge held in something similar to an electrical capacitor. A transistor acts as a gate in determining whether the value in the capacitor can be read or written. In static RAM, instead of a capacitor-held charge, the transistor itself is a positional flip/flop switch, with one position meaning 1 and the other position meaning 0.
Externally, RAM is a chip that comes embedded in a personal computer motherboard with a variable amount of additional modules plugged into motherboard sockets. To add memory to your computer, you simply add more RAM modules in a prescribed configuration. These are single in-line memory modules (SIMMs) or dual in-line memory modules (DIMMs). Since DIMMs have a 64-bit pin connection, they can replace two 36-bit (32-bits plus 4 parity bits) SIMMs when synchronous DRAM is used. Laptop and notebook computers contain smaller 32-bit DIMMs known as small outline DIMMs (SO DIMMs).
How Data Is Accessed
When the processor or CPU gets the next instruction it is to perform, the instruction may contain the address of some memory or RAM location from which data is to be read (brought to the processor for further processing). This address is sent to the RAM controller. The RAM controller organizes the request and sends it down the appropriate address lines so that transistors along the lines open up the cells so that each capacitor value can be read. A capacitor with a charge over a certain voltage level represents the binary value of 1 and a capacitor with less than that charge represents a 0. For dynamic RAM, before a capacitor is read, it must be power-refreshed to ensure that the value read is valid. Depending on the type of RAM, the entire line of data may be read that the specific address happens to be located at or, in some RAM types, a unit of data called a page is read. The data that is read is transmitted along the data lines to the processor's nearby data buffer known as level-1 cache and another copy may be held in level-2 cache.
For video RAM, the process is similar to DRAM except that, in some forms of video RAM, while data is being written to video RAM by the processor, data can simultaneously be read from RAM by the video controller (for example, for refreshing the display image).
How RAM Effectiveness is Measured
The amount of time that RAM takes to write data or to read it once the request has been received from the processor is called the access time. Typical access times vary from 9 nanoseconds to 70 nanoseconds, depending on the kind of RAM. Although fewer nanoseconds is better, user-perceived performance is based on coordinating access times with the computer's clock cycles. Access time consists of latency and transfer time. Latency is the time to coordinate signal timing and refresh data after reading it.
Kinds of RAM
RAM can be divided into (1) main RAM, which stores every kind of data and makes it quickly accessible to a microprocessor and (2) video RAM, which stores data intended for your display screen, enabling images to get to your display faster.
Main RAM
Main RAM can be divided into static RAM (SRAM) and dynamic RAM (DRAM).
Static RAM (SRAM)
Static RAM is more expensive, requires four times the amount of space for a given amount of data than dynamic RAM, but, unlike dynamic RAM, does not need to be power-refreshed and is therefore faster to access. One source gives a typical access time as 25 nanoseconds in contrast to a typical access time of 60 nanoseconds for dynamic RAM. (More recent advances in dynamic RAM have improved access time.) Static RAM is used mainly for the level-1 and level-2 caches that the microprocessor looks in first before looking in dynamic RAM.
Burst (or SynchBurst) Static RAM (BSRAM)
Burst SRAM (also known as SynchBurst SRAM) is synchronized with the system clock or, in some cases, the cache bus clock. This allows it be more easily synchronized with any device that accesses it and reduces access waiting time. It is used as the external level-2 cache memory for the Pentium II microprocessor chipset.
Dynamic RAM (DRAM)
Dynamic RAM uses a kind of capacitor that needs frequent power refreshing to retain its charge. Because reading a DRAM discharges its contents, a power refresh is required after each read. Apart from reading, just to maintain the charge that holds its content in place, DRAM must be refreshed about every 15 microseconds. DRAM is the least expensive kind of RAM.
Fast Page Mode DRAM (FPM DRAM)
Prior to newer forms of DRAM, Fast Page Mode DRAM (FPM DRAM) was the most common kind of DRAM in personal computers. Page mode DRAM essentially accesses a row of RAM without having to continually respecify the row. A row access strobe (RAS) signal is held active while the column access strobe (CAS) signal changes to read a sequence of contiguous cells. This reduces access time and lowers power requirements. Clock timings for FPM DRAM are typically 6-3-3-3 (meaning 3 clock cycles for access setup, and 3 clock cycles for the first and each of three successive accesses based on the initial setup).
Enhanced DRAM
Enhanced DRAM (EDRAM) is the combination of SRAM and DRAM in a single package that is usually used for a level-2 cache. Typically, 256 bytes of static RAM is included along with the dynamic RAM. Data is read first from the faster (typically 15 nanoseconds) SRAM and if it is not found there, it is read from the DRAM, typically at 35 nanoseconds.
Extended Data Output RAM or DRAM (EDO RAM or EDO DRAM)
Extended Data Output RAM (EDO RAM) or Extended Data Output Dynamic RAM (EDO DRAM) is up to 25% faster than standard DRAM and reduces the need for level-2 cache memory.
Burst Extended Data Output DRAM (BEDO DRAM)
BEDO DRAM improves page mode DRAM by "building in" three successive column address shifts after the first column address is specified so that four bits are read as a burst. Together with a dual-bank architecture, BEDO DRAM promised to offer 4-1-1-1 access times. However, because Intel and other manufacturers preferred SDRAM, BEDO DRAM was not widely used.
Nonvolatile RAM (NVRAM)
Nonvolatile RAM (NVRAM) is a special kind of RAM that retains data when the computer is turned off or there is a power failure. Like the computer's read-only memory (ROM), it is powered by a battery within the computer. It can also work by writing its contents to and restoring them from an EEPROM.
Synchronous DRAM (SDRAM)
Synchronous DRAM (SDRAM) is a generic name for various kinds of DRAM that are synchronized with the clock speed that the microprocessor is optimized for. This tends to increase the number of instructions that the processor can perform in a given time. The speed of SDRAM is rated in MHz rather than in nanoseconds (ns). This makes it easier to compare the bus speed and the RAM chip speed. You can convert the RAM clock speed to nanoseconds by dividing the chip speed into 1 billion ns (which is one second). For example, an 83 MHz RAM would be equivalent to 12 ns.
JEDEC SDRAM
JEDEC (Joint Electron Device Engineering Council) SDRAM is an industry standard synchronous DRAM. It has a dual-bank architecture and several burst mode accesses that can be preset. JEDEC SDRAM chips operate at either 83 MHz or 100 MHz. JEDEC SDRAM is also known as PC66 SDRAM because it was originally rated for 66 MHz bus operation and to distinguish it from Intel's PC100 architecture.
PC100 SDRAM
PC100 SDRAM is SDRAM that states that it meets the PC100 specification from Intel. Intel created the specification to enable RAM manufacturers to make chips that would work with Intel's i440BX processor chipset. The i440BX was designed to achieve a 100 MHz system bus speed. Ideally, PC100 SDRAM would work at the 100 MHz speed, using a 4-1-1-1 access cycle. It's reported that PC100 SDRAM will improve performance by 10-15% in an Intel Socket 7 system (but not in a Pentium II because its L2 cache speed runs at only half of processor speed).
Double Data Rate SDRAM (DDR SDRAM)
Double Data Rate SDRAM can theoretically improve RAM speed to at least 200 MHz. It activates output on both the rising and falling edge of the system clock rather than on just the rising edge, potentially doubling output. It's expected that a number of Socket 7 chipset makers will support this form of SDRAM.
Enhanced SDRAM (ESDRAM)
Enhanced SDRAM (ESDRAM), made by Enhanced Memory Systems, includes a small static RAM (SRAM) in the SDRAM chip. This means that many accesses will be from the faster SRAM. In case the SRAM doesn't have the data, there is a wide bus between the SRAM and the SDRAM because they are on the same chip. ESDRAM is apparently competing with DDR SDRAM as a faster SDRAM chip for Socket 7 processors.
Direct Rambus DRAM (DRDRAM)
Direct Rambus DRAM (DRDRAM) is a proprietary technology proposed by Rambus, Inc. in partnership with Intel. Like SLDRAM, it promises RAM speed up to 800 MHz. It has a smaller bus width (16 bits compared to 64 bits) than current SDRAM designs.
SyncLink DRAM (SLDRAM)
SyncLink DRAM is, along with Direct Rambus DRAM (DRDRAM), a protocol-based approach. In this approach, all signals to RAM are on the same line (rather than having separate CAS, RAS, address, and data lines). Since access time does not depend on synchronizing operations on multiple lines, SLDRAM promises RAM speed of up to 800 MHz. Like Double Data Rate SDRAM, SLDRAM can operate at twice the system clock rate. SyncLink is an open industry standard that is expected to compete and perhaps prevail over Direct Rambus DRAM.
Ferroelectric RAM (FRAM)
FRAM (ferroelectric RAM) is random access memory that combines the fast read and write access of dynamicRAM (DRAM) - the most common kind of personal computer memory - with the ability to retain data whenpower is turned off (as do other non-volatile memory devices such as ROM and flash memory). Because FRAMis not as dense (can not store as much data in the same space) as DRAM and SRAM, it is not likely replacethese technologies. However, because it is fast memory with a very low power requirement, it is expected tohave many applications in small consumer devices such as personal digital assistants (PDAs), handheld phones,power meters, and smart cards, and in security systems. FRAM is faster than flash memory. It is also expectedto replace EEPROM and SRAM for some applications and to become a key component in future wireless products.
In spite of its name, ferroelectric RAM does not contain iron. Today's FRAM uses lead zirconate titanate (PZT); other materials arebeing considered. The main developer of FRAM is Ramtron International.
Video RAM
Video RAM as "video RAM" means in general all forms of RAM used to store image data for the video display monitor. Somewhat confusingly, the most common type of video RAM is called Video RAM (VRAM). All types of video RAM are special arrangements of dynamic RAM (DRAM). Video RAM is really a buffer between the processor and the display monitor and is often called the frame buffer. When images are to be sent to the display, they are first read by the processor as data from some form of main storage RAM and then written to video RAM. From video RAM (the frame buffer), the data is converted by a RAM digital-to-analog converter (RAMDAC) into analog signals that are sent to the display presentation mechanism such as a cathode ray tube (CRT). Usually, video RAM comes in a 1 or 2 megabyte package and is located on the video or graphics card in the computer. Most forms of video RAM are dual-ported. While the processor is writing a new image to video RAM, the display is reading from video to refresh its current display content. The dual-port design is the main difference between main storage RAM and video RAM.
RAMDAC
RAMDAC (random access memory digital-to-analog converter) is a microchip that converts digital image data into the analog data needed by a computer display. A RAMDAC microchip is built into the video adapter in a computer. It combines a small static RAM (SRAM) containing a color table with three digital-to-analog converters (DACs) that change digital image data into analog signals that are sent to the display's color generators, one for each primary color - red, green, and blue. In a cathode ray tube (CRT) display, an analog signal is sent to each of three electron guns. With displays using other technologies, the signals are sent to a corresponding mechanism.
The SRAM part of the RAMDAC contains a color palette table. A logical color number in the digital data input to SRAM is used to generate three separate values obtained from the table - one for each of red, green, and blue - that are output to one of three digital-to-analog converters. The analog signal output from the converter is input directly to the display electron guns or other image projecting mechanisms. For displays with true color, the digital color data is fed directly to the DACs, bypassing the SRAM table, which is not needed.
Video RAM
Video RAM (VRAM) is the vanilla flavor of video RAM. It is dual-ported, allowing the processor to write to it at the same time that it is refreshing the image on the display monitor.
Synchronous Graphics RAM
Synchronous Graphics RAM (SGRAM) is clock-synchronized RAM that is used for video memory. It is relatively low-cost video memory. It uses masked write, which enables selected data to be modified in a single operation rather as a sequence of read, update, and write operations. It also uses block write, which allows data for background or foreground image fills to be handled more efficiently. SGRAM is single-ported. Its special features are what make it a moderately fast form of video memory. The Matrox Mystique is an example of a video card that uses SGRAM.
Window RAM
Window RAM (WRAM), unrelated to Microsoft Windows, is very high-performance video RAM that is dual-ported and has about 25% more bandwidth than VRAM but costs less. It has features that make it more efficient to read data for use in block fills and text drawing. It can be used for very high resolution (such as 1600 by 1200 pixels) projection using true color). It's used in the Matrox Millenium video card.
Multibank Dynamic RAM
Multibank Dynamic RAM (MDRAM) is a high-performance RAM, developed by MoSys, that divides memory into multiple 32 KB parts or "banks" that can be accessed individually. Traditional video RAM is monolithic; the entire frame buffer is accessed at one time. Having individual memory banks allows accesses to be interleaved concurrently, increasing overall performance. It's also cheaper since, unlike other forms of video RAM, cards can be manufactured with just the right amount of RAM for a given resolution capability instead of requiring it to be in multiples of megabytes.
Rambus Dynamic RAM
Rambus Dynamic RAM (RDRAM) is a video RAM designed by Rambus that includes a proprietary bus that speeds up the data flow between video RAM and the frame buffer. It's optimized for video streaming.
The RAM Table
RAM Technology
Application and Computer Location
Access Speed Range
Ports
Characteristics
Static RAM (SRAM)
level-1 and level-2 cache memoryAlso used in RAMDAC
Fast
One
RAM that is continually chargedMore expensive than DRAM
Burst SRAM (BSRAM)
Level-2 cache memory
Fast
One
SRAM in burst mode
DRAM
Main memoryLow-cost video memory
Slow
One
A generic term for any kind of dynamic (constantly recharged) RAM
FPM (Fast Page Mode) DRAM
Main memoryLow-cost video memory
Slow
One
Prior to EDO DRAM, the most common type of DRAM
EDO (Extended Data Out) DRAM
Main memoryLow-cost video memory
5-20% faster than FPM DRAM
One
Uses overlapping reads (one can begin while another is finishing)Currently, the most common type of DRAM
BEDO (Burst Extended Data Out) DRAM
Main memory and low-cost video
Faster than EDO DRAM4-1-1-1 at 66 MHz
One
Not widely used because not supported by processor chipset makers
EDRAM (Enhanced DRAM)
Level-2 cache memory
15 ns access to SRAM35 ns access to DRAM
One
Contains a 256-byte SRAM inside a larger DRAM
Nonvolatile RAM (NVRAM)
Preset phone numbers and profiles in modems
Fast
One
Battery-powered RAM
Synchronous DRAM (SDRAM)
Main memory
See specific forms of SDRAMRated in MHz rather than nanoseconds
One
Generic term for DRAMs with a synchronous interface
JEDEC Synchronous DRAM (JEDEC SDRAM)
Main memory
Fast
One
Dual-bank architectureBurst modeMost common form of SDRAM
PC100 Synchronous DRAM (PC100 SDRAM)
Main memory
Intended to run at 100 MHz with 4-1-1-1 timing
One
An Intel specification designed to work with their i440BX
Double Data Rate Synchronous DRAM (DDR DRAM)
Main memory
Up to 200 MHz
One
Activates output on both the up and the down part of the clock cycle, doubling the data rate of PC100 SDRAM
Enhanced Synchronous DRAM (ESDRAM)
Main memory
Fast (100 MHz +)
Two
Twice as fast as SDRAMSee Enhanced Memory Systems (EMS)
SyncLink DRAM (SLDRAM)
Main memory
Fastest (200 MHz +)
One
Open protocol-based designUses "packets" for address, data, and control signals
Direct Rambus DRAM (DRDRAM)
Main memory
Up to 800 MHz but with a 16-bit bus width
One
Backed by Intel and Rambus Inc.
Ferroelectric RAM (FRAM)
Main memory in small devices
?
?
Developed by Ramtron
RAMDAC
Video card
Fast
One
Uses a small SRAM to store the color palette table used to provide data for digital-to-analog conversion
Rambus DRAM (RDRAM)
Video memory for Nintendos
Up to 600 MHz
One
Intel and Rambus Inc. architecture
Synchronous Graphics RAM (SGRAM)
Moderate to high-end video memory
Closer to VRAM than DRAM
One
Has special performance-enhancing featuresExample: Matrox Mystique
VRAM (Video RAM)
Higher-cost video memory
Twice the speed of DRAM
Two
Dual-ported, meaning a new image can be stored in RAM while a previous image is being sent to the display
WRAM (Window RAM)
Less expensive video memory
25% faster than VRAM
Two
With RAMDAC, can handle true color at 1600 by 1200 pixel resolution
Multibank DRAM (MDRAM)
Low-cost high-end video memory applications
Faster
One
Interleaved memory accesses between banksMemory has multiple 32 kilobyte banks that can be accessed independentlyCan be manufactured to fit the amount of memory the card requiresNo size-related performance penalty


ROM
Pronounced rahm, acronym for read-only memory, computer memory on which data has been prerecorded. Once data has been written onto a ROM chip, it cannot be removed and can only be read.
Unlike main memory (RAM), ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile, whereas RAM is volatile.
Most personal computers contain a small amount of ROM that stores critical programs such as the program that boots the computer. In addition, ROMs are used extensively in calculators and peripheral devices such as laser printers, whose fonts are often stored in ROMs.
A variation of a ROM is a PROM (programmable read-only memory). PROMs are manufactured as blank chips on which data can be written with a special device called a PROM programmer .
Read-Only Memory or ROM is an integrated-circuit memory chip that contains configuration data. ROM is commonly called firmware because its programming is fully embedded into the ROM chip. As such, ROM is a hardware and software in one.
Because data is fully incorporated at the ROM chip's manufacture, data stored can neither be erased nor replaced. This means permanent and secure data storage. However, if a mistake is made in manufacture, a ROM chip becomes unusable. The most expensive stage of ROM manufacture, therefore, is creating the template. If a template is readily available, duplicating the ROM chip is very easy and affordable.
A ROM chip is also non volatile so data stored in it is not lost when power is turned off.
RAM versus ROM
Both RAM and ROM provide the user random access to stored data. However, RAM provides only short-term memory since data stored in RAM is lost when power is turned off. ROM, on the other hand, provides long-term storage since data is permanently etched into the ROM chip.
One other difference between the two is that RAM's data can frequently and speedily be altered and changed at will. ROM cannot be reconfigured at all.
ROM Chip Manufacture
The ROM chip has a matrix of columns and rows. The point of intersection between the column and the row is called a cell. Each cell will have a value of either 1 or 0. The manufacturer of the ROM chip has to determine each cell's value before the ROM manufacture ensues.
After the program has been designed, the ROM chip can now be made. At each cell where the value should be 1, a diode is placed to connect column to row. At each cell where the value should be 0, no diode is placed.
The ROM Chip's Diode
The diode is the cell's electronic check valve. Its main function in the ROM chip is to control and direct the flow of electric current in cells. Specifically, it transfers the electric current from column to row.
The diode has a minimum voltage requirement, what is commonly called the forward breakover, which needs to be surpassed before the diode will transfer the charge from the column to the row of the cell. The usual ROM diode forward breakover voltage is around 0.6 volts.
The ROM activates cells by sending through voltage that is more than the cells' diode forward breakover. The charge that is directed through the column gets passed on by the diode to the appropriate grounded row. Since charge is successfully transmitted from column to row, the cell where a diode is present has a value of 1.
In the ROM circuit, passing a charge through the column will not affect the cells whose values are supposed to be 0. In any cell, this charge cannot be passed from column to row if there's no diode to facilitate the transfer. Therefore, once a cell's value has been determined to be 0, it will permanently be 0.
How Graphics Cards Work
by Tracy V. Wilson and Jeff Tyson

Inside This Article
1.
Introduction to How Graphics Cards Work
2.
Processor and Memory
3.
Input and Output
4.
Choosing a Good Graphics Card
5.
Lots More Information
6.
See all Hardware articles
The images you see on your monitor are made of tiny dots called pixels. At most common resolution settings, a screen displays over a million pixels, and the computer has to decide what to do with every one in order to create an image. To do this, it needs a translator -- something to take binary data from the CPU and turn it into a picture you can see. Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card.
A graphics card's job is complex, but its principles and components are easy to understand. In this article, we will look at the basic parts of a video card and what they do. We'll also examine the factors that work together to make a fast, efficient graphics card.
The graphics card creates a wire frame image, then fills it in and adds textures and shading.
Graphics Card BasicsThink of a computer as a company with its own art department. When people in the company want a piece of artwork, they send a request to the art department. The art department decides how to create the image and then puts it on paper. The end result is that someone's idea becomes an actual, viewable picture.
Photo courtesy of HowStuffWorks ShopperThe four main components of a graphics card are connections for the motherboard and monitor, a processor, and memory.
A graphics card works along the same principles. The CPU, working in conjunction with software applications, sends information about the image to the graphics card. The graphics card decides how to use the pixels on the screen to create the image. It then sends that information to the monitor through a cable.
The Evolution of Graphics Cards
Graphics cards have come a long way since IBM introduced the first one in 1981. Called a Monochrome Display Adapter (MDA), the card provided text-only displays of green or white text on a black screen. Now, the minimum standard for new video cards is Video Graphics Array (VGA), which allows 256 colors. With high-performance standards like Quantum Extended Graphics Array (QXGA), video cards can display millions of colors at resolutions of up to 2040 x 1536 pixels.
Creating an image out of binary data is a demanding process. To make a 3-D image, the graphics card first creates a wire frame out of straight lines. Then, it rasterizes the image (fills in the remaining pixels). It also adds lighting, texture and color. For fast-paced games, the computer has to go through this process about sixty times per second. Without a graphics card to perform the necessary calculations, the workload would be too much for the computer to handle.
The graphics card accomplishes this task using four main components:
· A motherboard connection for data and power
· A processor to decide what to do with each pixel on the screen
· Memory to hold information about each pixel and to temporarily store completed pictures
· A monitor connection so you can see the final result
Next, we'll look at the processor and memory in more detail.


NEXT
Inside This Article
1.
Introduction to How Graphics Cards Work
2.
Processor and Memory
3.
Input and Output
4.
Choosing a Good Graphics Card
5.
Lots More Information
6.
See all Hardware articles
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