Computers uses video memory to generate and display 3-D graphics on the monitor. Video memory is a form of RAM that uses binary data required for 3-D playback. This graphics capability either comes built into the motherboard or through a graphics or video card. Depending on its 3-D graphics capability, your computer may have to draw on its own RAM to meet its video memory needs. This creates the need for shared memory, in which case, the computer's CPU and graphics chip will share the RAM. You can configure shared memory through your computer's BIOS settings.
Boot the computer and enter the BIOS settings screen by pressing the appropriate function key or keys during the boot-up process. The key varies by computer manufacturer but it is often the F1 or F2 key.
After accessing the BIOS set up, select Advanced and then choose the Integrated Peripherals menu and select the option for AGP aperture size. Under this option, you can now allocate a specific amount of RAM for shared video memory. Select an amount ranging from 8MB to 64MB RAM. On newer PCs, you can allocate more RAM for video memory; for example, 128MB or 256MB.
Save the changes, exit the BIOS settings screens and wait for the computer to starts its operating system. Your PC now has a shared memory, with a portion of its RAM allocated for video memory and the rest used by the CPU.