Nvidia aims to help out the multitude of people stuck in that exact situation. With their previous GPU architecture, Nvidia introduced TurboCache technology, at first with their GeForce 6200 card. TurboCache allocates system memory to the video card by way of the PCI Express interface, and while it's certainly not as desirable as having copious amounts of high-speed on-board RAM, it is a useful way of adding more effective total frame buffer memory to an entry-level card, while also keeping prices down.

Read Here