I have an S3-928 based VLB video card and have been running it
for a while with no problems with 32MB of system RAM and XFree86's
XF86_S3 mmio_928 driver. However, when I upgraded to 64MB of system
RAM, X stopped working, and I got kernel panics even when I didn't
run X.  I decided that the problem was that the video card mapped
itself into RAM below the 64MB mark and the system was getting
confused. When I dropped back to 48MB, things were fine. At the
moment I am running successfully by adding BIOSEXTMEM=60416 to my
kernel options, but this seems like a sledgehammer tactic since
I never know when I'll have to pull out a SIMM for some reason.
There doesn't seem to be any way to map out RAM via my system's
BIOS.
   Could/should NetBSD deal with this situation by detecting the
card, finding the RAM area that it is using, and mapping out that
area of usable RAM? This seems to be a weakness in having video
resources managed at user level.

                                      Gary D. Duzan
                         Humble Practitioner of the Computing Arts