Video Monitor CRT: Cathode Ray Tube The screen is coated with tiny dots of phosphor material, called pixels, that glow when electrically charged. Electron beam moves back and forth, working top to bottom and left to right one row at a time, lighting up phosphor dots on inside of tube

Refresh rate Speed with which a monitor redraws images on the screen Time it takes for electron beam to paint the screen from top to bottom expressed in Hertz, e.g., 70 Hz= 70 times per second the higher the refresh rate, the less flickering and the easier on your eyes

Interlacing Interlaced monitors draw the screen in two passes- even lines on the first pass and odd on the second pass lower quality- more flicker than noninterlaced

Shadow mask monitor Shadow mask metal screen with thousands of tiny holes

Resolution Resolution= number of pixels monitor can display. Number of horizontal pixels x number of vertical pixels, e.g., 640 x 480 means 640 pixels in each horizontal row, 480 vertically Higher resolution means a greater number of pixels display and smoother image

Dot pitch Dot pitch is a measure of image clarity Represents the distance between each pixel. The smaller the dot pitch, the clearer the displayed image. Expressed in millimeters, e.g., .28 mm, .25 mm, etc.

Video Cards Video card converts digital output into an analog video signal sent through a cable to the monitor. Composed of video RAM and video processor in modern cards (older cards did not have a video co-processor and used CPU for these calculations- MUCH slower!)

Types of Video memory VRAM- Video RAM- requires less refresh than regular DRAM WRAM- Windows RAM- faster than VRAM SGRAM- Synchronous Graphics RAM- very fast!, because it’s synchronized to system clock (like SDRAM)

How much video memory? A video card must have enough RAM to draw image on screen To calculate how much video RAM is required for a given resolution and number of colors (see Gilster p. 202): 1. Multiply the desired resolution x number of color bits 2. Divide product by 8

Video modes: MDA: Monochrome Display Adapter- old! CGA: Color Graphics Adapter 320x200 (4 colors) or 640x200 (2 colors) EGA: Enhanced Graphics Adapter (EGA) 16 colors, resolution of 640x350

Video modes continued VGA: Video Graphics Array 640x480, 16 colors (256 colors at lower resolution) Super VGA: up to 1280 x 1024 and up to 16 million colors

Monitor connectors 15-pin VGA connector is standard monitor and video card connector 9-pin used in older monitors (CGA, EGA, early VGA) BNC connectors used in some high-end monitors

Monitor safety The monitor uses more power than the rest of the computer put together and produces very strong electromagnetic emissions (20,000 volts, even when power is off!) Best to avoid working on monitors- never use ESD grounding strap with monitor Energy Star standard: EPA program to reduce monitor energy consumption by 99 percent in suspend mode