On i386/DX20, Hayes ESP board in 16550 mode.

vm_fault, Page Fault Trap

_Xintr4()
_comintr(f866af80)	0x214
_slstart(f867b200)	0x3a
_comstart(f867b200)	0x90
_bcopy(f867b240, f7bffc0c, 10, f866af02, f867b240)	0x3d

_bcopy	0x3d	repe movsl  (%esi),%es:(%edi)

This is as much of a dump as I was able to obtain.
>Please send the *exact* text from the kernel.

I'm waiting for another trap into the debugger, but all I've 
seen is a few spurious reboots with no messages trapped.  I've
added log diagnostics to watch for odd values in and about the
q_to_b call, but nothing very interesting so far.