[ The PC Guide | Systems and Components Reference Guide | Video Cards | Video Memory Function and Speed ]

Memory Size and Memory Access

There is an important impact on video performance when using a 64-bit video card. A card that is 64 bits is called this because the video memory is accessed 64 bits at a time. Many of these cards use banks of memory that are 32 bits wide. If you put 1 MB of DRAM in a card like this, it is organized as 256Kx32. If you put 2 MB in, it is 256Kx64.

What this means is that if you use many types of 64-bit video cards with only 1 MB of DRAM, the card is forced to access the memory only 32 bits at a time, which greatly reduces video bandwidth. If you add another 1 MB of memory the performance of the card actually increases. This is a rare situation where adding more memory to a video card actually increases performance (as opposed to just allowing higher resolution).

Next: Video Memory Technologies

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