X11 expertise on ancient HW sought... (4-plane visual (overlay) via X-server on MS-WIndows)

[...] Only for values of "cannot" that are more like "do not bother to include the software to", I would say. "Visual" is a technical term in X. I don't know whether Windows has a corresponding abstraction, so I don't know whether there is anything it calls them. No. However, it is substantially more difficult for an X server to present a visual that the hardware doesn't support, which is probably why the server you have doesn't do it. Well-behaved clients must be prepared to handle whatever capabilities the server presents; the problem here is that the client you have handles the server you have by complaining and dying. Depending on what other capabilities the client is using, you might be able to get the overlay effect using colourmap hackery with comparatively small code changes. What PseudoColor or DirectColor visuals are available? Read the documentation, of course, or contact the manufacturer's support department. You may be out of luck without repalcing the hardware, then. (That's one of the prices of buying undocumented hardware....) You probably do not need a GPU. The era when 4-bit visuals were common was full of dumb memory-mapped framebuffers; modern CPUs are fast enough that they can probably fake up a 4-bit overlay visual and still run at least as fast as the hardware your client software was designed to run against. I'm not sure how hard it would be to do. My X server hackery has never included faking something the hardware doesn't support, so my experience is rather limited in that direction. But I've done DDX layers for at least three widely disparate framebuffers, and I feel reasonably confident what you want could be done. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mouse at rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B