This is somewhat of a controversy.  2 years ago any video card with 32 MB of
memory (possibly even 16) would be quite capable to support both the frame
buffer and the texture cache of any game.  However with the new generation
of software that is now coming out, more and more memory is need to store
the (much) larger textures used in 3D games.  First of all, the new games
use larger textures around the 480 - 512 pixels (sq) range.  Secondly, they
are now starting to use 32-bit textures (16 million colors) as apposed to
the previously used 16-bit (64,000 colors) and 8-bit (256 colors).  So you
have more pixels and more colors that are pushing the envelope on texture
cache size.

AGP 2x and 4x is the speed rating at which the video card can access system
RAM.  AGP texturing is the only functional use of this feature, although
some card manufacturers still fail to make use of it (such as the new addax
Voodoo3 cards, none of which support AGP texturing).

As an example, Quake 3 - Arena will offer textures at 512x512 @ 32-bit color
(Voodoo 3 cards will have to downsample both the size and the color-depth of
the textures, as they do not support 32-bit (external) rendering).  One
512x512 texture map @ 32-bit color is 1 MB.  In a typical 3d game, there are
NUMEROUS on screen object at any given time.  If your have a 32 MB card, you
will be using probably a 4-8 MB frame buffer and the rest on your texture
cache.  If you only have 24 MB of RAM left on your card, you can only have
24 textures on-screen, which is not a lot if you figure that most games now
use both multi-texturing and bump-mapping.  So in effect, each object can
have 3 or more textures applied to it, which now brings us down to 8
onscreen objects (8 objects x 3 textures = 24 MB RAM).  The card uses AGP
texturing to make use of extra system RAM to provide more texture
capabilities.  This will be more important as games continue to use larger
(and more) textures...I fully expect to see 48/64/72/96 MB configurations on
consumer-level video cards within the next few years...we are already at
32MB with the ATI Rage Fury and Nvidia TNT2...

Hope this helps,

Brad Boutwell
BDB Graphic Design
Tulsa, OK

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