How do video cards work?

Video cards come with there own ram, say 128mb, does that computer only use this and that's all or if it needs more to process something, will it tap into it's own ram. If you have more computer ram, like a gig, and a crappy 64mb card, would that run better than only haveing 128mb or ram, with a 64mb card? Thanks, sorry to be so confusing.

How do video cards work?
Having more system memory may increase graphics accelerator performance if and only if the graphics accelerator used shared system memory. That is, the graphics card used the same memory that the system uses. This way, as you acquire more RAM, you can set the graphics memory higher. This is only common on laptop graphics though, not on desktops. Also, any good graphics accelerator has it's own dedicated memory.





The reason graphics accelerators have their own memory, is so that when the graphics processor needs to retrieve some data, it only needs to goto it's local memory. If it had to go to system memory, then it would take much longer to retrieve the data and would slow everything down. Such is known as a bottleneck.