You do need to consider buffers. At 640x480 resolution and 16-bit color, double-buffering, the minimum allowed, uses 1.2 MB video memory. 1024x768 at 32-bit color triple-buffered, in contrast, uses 9 MB video memory in just buffers alone. Then there's textures as well that also get stored in video memory. Thus, games could run on just 4 MB video memory. You wouldn't get the level of detail of even semi-decent low-quality, small levels, but is sufficient for certain circumstances (such as prerendered scenes) and simple games (like bowling or some simple marble game).