Lenovo PC 300GL Understanding Your Personal Computer 6267, 6277, 6287 - Page 21

row from top to bottom, then starts at the top to fill in the rows that were skipped on the first pass. The noninterlaced method draws the complete image on each pass. The vertical refresh rate affects the stability of the image on the screen. Monitors that have a fast, noninterlaced refresh rate provide a very stable image with little or no detectable flicker. Monitors with slower refresh rates tend to have more noticeable flicker. Flicker can be particularly noticeable with white and other light-colored backgrounds. You can minimize flicker by changing the colors you work with. Many programs allow you to select colors. Sensitivity to flicker varies from person to person. Noninterlaced flicker occurs when the screen is redrawn at a rate that is slow enough to be detected by the human eye. Interlaced flicker, or jitter, occurs when the pattern of pels in adjoining lines is very different, or when an object on the screen is made up of alternating bright and dim lines. Some application programs cannot reproduce all colors and use a technique called dithering to combine two colors. For example, light red might be produced by alternating lines of white and red. As the image is continually refreshed using the interlaced method, the red lines are drawn on one pass and the white lines on the next pass. As a result, the light-red object might appear to flicker while the rest of the image on the screen remains stable. DDC Protocol Potential problems with monitor flicker are reduced by operating a monitor at its highest refresh rate. To simplify the job of setting the refresh rate, some monitors offer Plug and Play capability using the VESA Display Data Channel (DDC) protocol. DDC is an industry standard for passing configuration information between a monitor and a computer. Both the monitor and the computer must have DDC capability. Your computer supports the DDC2B protocol. With DDC, the computer can receive configuration information sent from a DDC monitor. When you turn on the computer with a DDC monitor connected, the monitor immediately starts sending its identification information to the computer. This information, called Extended Display Identification Data (EDID), includes a description of the monitor and its operational limits and timings. The POST programs use the information from the monitor to automatically configure the video controls to operate the attached monitor in its optimum mode. Thus, when the monitor comes on, it is already set to the highest refresh rate that the monitor and graphics controller can support. Power Management Power management reduces the power consumption of your computer when you are not using it. A monitor with VESA Display Power Management Signaling (DPMS) support can save a significant amount of energy and have a longer useful life. DPMS-compliant monitors can be powered down in three modes: Standby, Suspend, and Off. The stages that can actually be used, however, depend on the power-management capabilities of your computer. Video 13