This is HankNV--better known as HangNV by the friendly NVIDIA Developer Zander, pander, dander, or something like that. I guess he's a developer. Good thing he's not a diplomat.
But yeah, the Voodoo 3dFX works like a charm. It's just slower than the MX400--even when the AGP is disabled. Of course, all the voodoo cards run no faster than AGP 1X anyway. I'm running the same card on a SuperMicro Dual CPU board and I have to disable the AGP to get it to run without going into a black screen.
If you can get to a terminal, I would try (this is just a suggestion and not a fully qualified developer's comment) changing the agp setting so it's disabled.
Option "NvAGP" "0"
That's the only way I got mine to work.
I gave up trying to get the AGP to work after NetLlama suggested that it was a kernel related AGP bug and had nothing to do with the driver. Actually, I haven't given up yet. I'm trying to go backwards and find a working 2.4 kernel that will take advantage of the AGP setting. This card really flies when everything's working. I used to have it working about a year ago. Should have left it alone.