Video Memory

Just as the CPU uses memory on the motherboard as a workspace to create information, the video card uses its own video memory (or main memory borrowed by systems with integrated graphics) as a place to create visual information that is displayed by the monitor. Just as different types of RAM affect the speed of the computer, different types of video RAM affect the speed of the video card.

Video memory comes in almost as many different types as motherboard memory. The following types of memory were reviewed in Chapter 7, "RAM," and their performance on video cards is comparable to their performance on the motherboard:

• DRAM ” Dynamic RAM

• EDO RAM ” Extended Data Out RAM

• SDRAM ” Synchronous DRAM

• DDR SDRAM ” Double Data Rate SDRAM

At one time, video cards could be expanded with additional memory, just as motherboards have been for many years . However, rapid changes in video card technology and lower-cost production methods have practically eliminated upgradeable video cards.

If a video card needs more memory, you need to yank it out and replace the card because there's no place to add memory to most recent models. Use a model that has more memory plus other advanced features (such as a faster graphics chip and dual-display support) as a replacement.

Of these four memory types, DDR SDRAM is the fastest and is extremely common on new high-performance video cards; because it is a variation on standard SDRAM (popular for lower-priced video cards), video card makers can easily adapt their designs to use it. DRAM and EDO RAM were often found on older video cards.

Special types of video memory have also been created for the needs of video display:

• Video RAM ( VRAM ) enables data to be read from it and written to it at the same time; this type of operation is referred to as dual ported . Video RAM is very fast when compared to DRAM but has not proven to be very popular.

• Window RAM (WRAM ) is a modified version of VRAM. WRAM is also very fast when compared to DRAM but is not very popular.

• Synchronous Graphics RAM (SGRAM ) is a faster version of SDRAM with additional circuitry designed especially for video cards. It is very popular on many recent high-performance video cards.