testing an ati 28800-5 wonderxl(comes with 512kb and i have filled up to 1mb), and encountered following issues:

in dos, univbe detects it but would only support up to 800*600*256c and 640*480*15bpp modes, no 1024*768*256c or 800*600*15bpp modes.

in windows98, i used the built-in ati vga wonder driver, and i can see hicolor modes in the [ativga] section of the dxati.inf file. but in windows it would go up to 800*600*256c only, with no 15/16bpp options at all.
strangely there is a 24bpp option instead, which is probably reserved for the truecolor wonderxl24 and doesn't work with my card of course. attempting to choose 1024*768*256 resolution failed aswell.

does anyone have memory of such problems, and workarounds(including driver updates)?