This creates a problem when the two applications appear on different windows of the same screen. The original VGA display had a resolution of 640x480 and supported 4 bit color. This required only 256K of memory. An SVGA adapter with 1 megabyte of video memory can support 1024x768 resolution at 8 bits, or 800x600 resolution at 16 bits. In some systems, it can also display 1280x1024 in 4 bit color.
Additional memory is required for greater resolution or more color depth.
The Refresh Rate determines the speed that the display uses to paint the dots on the screen. The original VGA displays ran at 60Hz, but some people complained that this produced a flicker. International standards now require a rate of 70Hz. Everyone knows that you cannot reliably run a CPU chip rated for 166 MHz at a speed of 200 MHz. However, video systems come with a variable clock rate.