Video RAM question

[not important]

I was looking at some low end PCI-EX16 video cards and the phrase "Supporting 512MB (Onboard 256MB 64-bit DDR)" keeps popping up up. Could someone explain just what this means?

[ski]

That means that a video card with 256 MB of onboard RAM can borrow up to an additional 256 MB of system RAM, or a total of 512 MB for graphics use.
Nvidia's Turbocache architecture uses this technology in a manner that's supposed to enable faster performance than a non-Turbocached video card/adapter.

[RazorDX]

Uses the same concept as onboard graphics. Basically it has very minimal graphics memory, and sucks your main system memory instead. Sure, it can make your graphics card faster... but the rest of your system suffers. Unless you have over 1.5GB of RAM, it doesn't really increase your speeds.

[not important]

That's was my assumption. Thanks for the replies.