Don't forget how much higher screen resolutions are these days. Color depth also. Those 8 MiB systems were driving single-buffered displays with perhaps 800x600 resolution at eight bits per pixel, with a color palette and dithering, which requires about 480 KB to hold the framebuffer image. Most applications would render directly into the framebuffer. A full HD (1080p) screen at 32 bits per pixel requires 8 MiB just to store the framebuffer (16 MiB with double-buffering), and that's not counting any of the input data or code needed for rendering. Figure on two or three times that to hold separate textures for each window (depending on the window sizes and how much they overlap) so that they can be composited live with desktop effects.
Comments
Don't forget how much higher screen resolutions are these days. Color depth also. Those 8 MiB systems were driving single-buffered displays with perhaps 800x600 resolution at eight bits per pixel, with a color palette and dithering, which requires about 480 KB to hold the framebuffer image. Most applications would render directly into the framebuffer. A full HD (1080p) screen at 32 bits per pixel requires 8 MiB just to store the framebuffer (16 MiB with double-buffering), and that's not counting any of the input data or code needed for rendering. Figure on two or three times that to hold separate textures for each window (depending on the window sizes and how much they overlap) so that they can be composited live with desktop effects.