The Socket X initiative, announced in May 1998, was an ill-fated attempt by Micron, Rendition and a few others to make video-board-on-a-chip in the same manner as microprocessors. They're reasoning was that silicon etching technology had advanced enough to the point where large amounts ('large' meaning 8 megabytes in 1998) of VRAM could be embedded in a chip along with the graphics logic. This would allow manufacturers to put graphics capabilities on a motherboard without fear of them become outdated too quickly -- when you need more, just swap out the chip!
It had its upsides, like VRAM being coupled to the chip with 256- or 512-bit busses. While it was an interesting design, but in order to really make it fly, they would have to create an completely new design with as much logic as the motherboard itself -- with voltage controls, bus speeds and the like. And the payoff was not guaranteed.
So in late 1999, Rendition had become an 'also ran' in the graphics game, and Micron wanted focus on its DRAM market, so the initiative was officially dropped.