How the graphics card works

how the graphics card works　
the data after the CPU processing must undergo the following 4 steps before it reaches the display:
1. 　From bus to GPU (graphics processing Unit, graphic processor): The data sent by the CPU is sent to the North Bridge and then sent to the GPU (graphics processing device) for processing. 
2. 　Enter video RAM (video memory) from video chipset (graphics chipset): The data processed by the chip is sent to the video memory. 
3. 　From memory to digital Analog Converter (= RAM DAC, Random read-write memory-to-analog converter): reads data from the video memory and sends it to the RAM DAC for data conversion (digital signal to analog signal). 
4. 　Enter the monitor from the DAC: the converted analog signal is sent to the display. 
display performance is a part of the system performance, its efficiency is determined by the above four steps, it and the performance of the card (video performance) is not the same, if you want to strictly distinguish,
The performance of the display card should be determined by two steps in the middle. because this two-step data transfer is in the inside of the display card. 
The first step is the CPU (the machine and the controller together the core of the computer, called the microprocessor or central processing unit) into the display card, the final step is to send the data directly from the display card to the display.
RAM DAC (typically integrated inside the graphics accelerator)

RAMDAC (random Access memory Digital-to-analog Converter). The Chinese name is a digital-to-analog converter. The role of RAMDAC is to convert digital image data into computer-displayed analog data. The display receives an analog signal after RAMDAC processing. Since the RAMDAC is a single, irreversible circuit, the analog signal after RAMDAC processing can no longer be converted into a digital signal. The RAMDAC is the most important device that affects the performance of the display card, which determines the maximum resolution and refresh rate that can be supported by the display card in sufficient memory. The role of RAMDAC is obvious, in the actual use, RAMDAC performance is important? Some friends may think of these problems, because today's graphics accelerator cards are labeled with how many Hz RAMDAC. The RAMDAC clock is fast (HZ) and the table can handle a higher refresh rate. Refresh rate refers to the number of times per second to redraw the screen, the person's eyes at less than 75 of the refresh rate will feel flicker, thus affecting the normal use and vision, in order to protect our priceless eyes, good graphics accelerator not only to ensure that the color number is very high, but also to ensure a higher refresh rate. So with the better (faster) performance of the RAMDAC, this graphics accelerator card can provide higher resolution, color depth and refresh rate, graphics accelerator card performance is better. That's why today's graphics accelerator card Ramdam clocks are getting faster. What does a friend who looks at the above may want to RAMDAC? Can I find it on the graphics accelerator card ? I'm afraid the problem is going to disappoint my friends. Today's graphics accelerated chip production process is getting better, RAMDAC have been integrated into the graphics accelerated chip, so we see the graphics accelerator is only memory and a main chip, and do not see the RAMDAC chip. However, there are some exceptions, such as professional-grade drawing cards. Due to its own design, RAMDAC is a separate chip.   Imaging Problems in the RAMDAC, the digital expression of the RGB color channel is converted to a VGA drive voltage by a D/a converter, the VGA drive voltage is transmitted to the CRT and then amplified into the electronic gun high-speed electronic flow, the electron stream bombardment screen phosphor glow and display the image. Because the RAMDAC integrated in the display chip inside, each manufacturer display chip design is different, so the display effect also has the difference. An important part of the effect of the display is the RAMDAC color-voltage table, such as the red color channel in the most intense color pairs should be the maximum channel voltage, the most light color represents the channel minimum voltage, the maximum voltage and the lowest voltage difference determines the color range, I think ATI RAMDAC maximum/ The difference of the minimum voltage is greater than that of NV, and its differential filter circuit is good for smoothing the voltage difference, so that the color contrast is large (clear) and the color transitions smoothly (less image color blocks).   Low-pass filter circuitThe low-pass filter circuit is only allowed a certain frequency below the signal through the circuit, usually the bandwidth of the video signal in a few MHz to about 10 MHz, generally we just let the useful signal through it, the higher or lower frequency signal is not what we want, can be understood as noise, The low-pass filter circuit is to remove these unused signals, otherwise the 2D display quality will be reduced. The low-pass filter circuit is usually located in the circuit board near the VGA plug, consisting of a transistor amplification circuit and a capacitor/resistor filter circuit, the transistor amplification circuit is to amplify the VGA signal to counteract the signal attenuation caused by the capacitance/resistance filter circuit.

How the graphics card works