I've managed to get Win98SE running games in software mode with pretty decent performance using DosBox Daum 2013-05-06. I can also get them set up for Glide with equally good results as long as I use certain settings.

The problem is that it requires using output=opengl, and all of the Daum builds I've tried have issues with opengl in fullscreen while running Windows. The only one that seems to work as intended is the latest build, but the performance is very slow.

Has anyone managed to set up 3DFX/Glide/Voodoo games in Win9x and DosBox fullscreen?