How a Graphics Card Works: Images from Electrical Signals Matt Kuraska
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How a Graphics Card Works: Images from Electrical Signals Matt Kuraska 25 March 2015 Figure 1: Graphics Card (Photo From: www.tomshardware.co) 1 Audience and Scope The purpose of this document is to educate readers by explaining the technological functions that occur within a computer’s graphics card. This guide will serve only as a general learning tool and will not specifically describe how a certain commercial product works. Each process defined within this document will, however, apply to most machines because the technical components are typically the same among all computers with slight deviations in laptops. This paper will discuss the electronic aspects that allow this one mechanical piece to create images on the screen, but also will encompass how it interacts with other essential parts in the machine. After reading this document, audiences will learn exactly how a graphics card functions within a desktop computer. The intended audience for this document includes high school and college students that are interested in Computer Science or Information Systems. This guide will supply readers with an in-depth understanding of a graphics card which will benefit their pursuit of further education in technology. An Introduction to Graphics Cards A graphics card is an essential component within a computer that takes input from binary code (ones and zeroes in a specific pattern) then translates these instructions into different colors that apply to every single pixel on the monitor’s screen. A monitor with a resolution of 1680 x 1050 contains a total of 1,764,000 pixels. The graphics card has to apply a color to each one to portray an image. In the case of a video, this device has to constantly change these pixels, which requires numerous computations every second. Binary Code from CPU (processor) | Graphics Card Translates | Image Appears on Screen Figure 2: Basic Function of Graphics Card (Images from: carlraoul.blogspot.com | pc-internet-zone.blogspot.com | configurareequipos.com) 2 Fundamentals of a Computer Before getting started and focusing on the graphics card, it is important to have a background of understanding about how a computer functions as a whole. We will focus on desktop computers, because laptops tend to be slightly more complex in their makeup. First of all, the computers we use are made from various different mechanical parts that piece together and form a working machine. Every section within the case of a desktop can be dissected and broken down to a microscopic level of circuits and miniscule wires creating an information pathway throughout the computer. The main mechanisms include: Central Processing Unit (CPU) which serves as the “brain” of the machine Hard Drive which stores all your software Random Access Memory (RAM) allows the computer to process multiple tasks simultaneously Graphics Card that converts signals into images on the screen Motherboard which is the main circuit board All of these pieces are considered the hardware of a computer, while the virtual programs and information are referred to as software. External parts such as a mouse and keyboard are called input and output devices (I/O) that send information to the computer and tell it where to move the cursor or what buttons are being pressed. The monitor serves as a recipient of information and displays the results of the user’s commands. Computer screens are made up of numerous tiny dots called pixels. Each pixel has a specific color value that creates an image when put together, similar to a mosaic painting. Graphics Card Composition Once we look deeper at the parts of our machine, we can see that the graphics card has a unique composition of its own which is just as complex as the computer, itself. Laptops tend to have their video cards “integrated” into the motherboard which means it shares information with the CPU, so we will focus on the standalone version that is found in most desktops. Parts: Connection Interface (Bus) Video Chip (GPU) RAM DAC Circuit Board The connection interface, also known as the “bus” connector, typically looks like small teeth with grooves on the edge of the video card. This piece connects to the motherboard so it can interact and receive information from the central processing unit. The video chip is responsible for manufacturing the particular signals in order to create the desired image. The memory (RAM) on a graphics card is dedicated strictly to holding information required to output images 3 on the screen. By separating this from system RAM, the processor will not be overloaded with information and the computer can run smoothly. The digital to analog converter (DAC) exists on the graphics card to convert the signals from the video chip into a form that the monitor can understand. This tends to be connected through the use of a 15-pin VGA cable, which most users will identify as the cord with blue ends that plugs into their monitor from the back of their desktop. Graphics Card Functions Information flows through a computer by means of the central processing unit, but not in any language humans use to communicate. In computers, data is stored and transported in the form of binary code, which means that every command comes in the form of ones or zeroes that string together and form “words” that the machine can understand. The graphics card receives information in this form through the bus connection with the motherboard and CPU, then uses the video chip to discern what colors the computer wants to input for each pixel. Every frame or image on the screen is the result of a “bit map,” a series of binary digit codes (Bourke). In a monitor displaying 60 frame per second (fps) the graphics card has to make 60 cycles of binary digits every second. To make this process run smoother, the RAM within the video card stores the information necessary to make the next image to put on screen. Monitors, however, do not read information in binary code. Instead, they accept analog signals. The DAC serves to solve this problem by translating the binary form of the bit map to an analog signal that the screen can accept and then produce the designated image successfully (Tyson). Figure 3: Information Transportation through Graphics Card (Image from: karbosguide.com) 4 Conclusion The graphics card is an essential part of a computer that allows images to be displayed on the screen. In order for this to happen, it must receive information from the central processing unit by means of the bus connection with the motherboard. From here, the video card must apply a color to each pixel on the monitor to create the desired picture. Typically, the machine must make these calculations multiple times every second to ensure a smooth video. Initially, the information for the images exist as a bit map of binary digits. The video card must then translate this digital signal into an analog signal before it reaches the monitor. Graphics cards are present in numerous machines today including cell phones and video game consoles which operate similarly to those in computers. 5 Works Cited Bourke, Paul. "A Beginners Guide to Bitmaps." A Beginners Guide to Bitmaps. N.p., Nov. 1993. Web. 25 Mar. 2015. Karbo, Michael B. "The Video Card." An Illustrated Guide to the Video Cards. Web. 25 Mar. 2015. Tyson, Jeff. "How Graphics Cards Work." How Graphics Cards Work. Mind Pride Computer Services, 21 Nov. 2007. Web. 23 Mar. 2015. 6 .