I'm forwarding this one in the hopes that someone will figure out where
the problem is.  I believe that I've heard several complaints like this
one regarding recent kernels and NuBus video:

SUNAGAWA Keiki wrote:

> Hi, Colin.
> 
> Colin> So the above was a result of using the 13" monitor???
> Colin> What color mode are you booting in?  What does a 'trace'
> Colin> in the debugger say at this point?
> 
> Unfortunately, my own (1.2G) kernel did not work with NuBUS
> video card for me though internal video is ok.  Here is the
> result:
> 
> When I ran startx, kernel hang.  This is the message.
> 
> vm_fault(123000, ddddd000, 1, 0) -> 1
>   type 8, code [mmu,,ssw]: 401074d
> trap type 8, code= 401074d, v= dddddde5
> kernel: MMU fault trap
> pid = 172, pc = 0009932A, ps = 2001, sfc = 0001, dfc = 0001
> Registers:
> [Register dump]
> Kernel stack (0083AD24):
> [stack dump]
> panic: MMU fault
> stopped at	_Debugger+0x6:	unlk	a6
> db>
> 
> When I hit t(return), ddb said:
> 
> _Debugger(1,83aed60,c59d0,c55c7,13001000) + 6
> _punic(c55c7,13001000,0,13000000,0) + 40
> _trap(8,401074d,dddddde5) + 1ee
> faultstkadj(123108,13000000,83ae50) + 0
> _vm_map_mageable(123108,13000000,13001000,0) + 68
> _pmap_enter(6c67d00,74000,4ec0000,5,0) + 160
> _vm_fault(6c41700,74000,1,0) + ba2
> _trap(8,402f209,74748) + 4f0
> faultstkadj() + 0
> db >
> 
> Any hints?  It's only on me?
> 

Later.

Colin