Say, I just got nailed with this crash on my AXPpci33 (166 MHz). I
swap to drives sd0 and sd1, and that I had just started a build of
inn from pkgsrc. This is with a 1.5 kernel (which I have now replaced
with a 1.5.1 kernel).

My first guess would be that the drive failed reading block 13376
(which would fall in the swap space partition) and the failure cascaded
into a sudden reboot. 

Why would failing to swap in a process cause a panic, a machine check,
and then a failure to dump?

Another theory of mine is that the memory in this box is flakey. *shrug*



sd1(siop1:2:0):  Check Condition on CDB: 0x08 00 34 40 10 00
    SENSE KEY:  Media Error
   INFO FIELD:  13376
 COMMAND INFO:  8192 (0x2000)
     ASC/ASCQ:  Scan Head Positioning Error


fatal kernel trap:

    trap entry = 0x3 (instruction fault)
    a0         = 0x4
    a1         = 0x1
    a2         = 0x0
    pc         = 0xfffffc000015f9c4
    ra         = 0xfffffc000015f9c0
    curproc    = 0xfffffc0000663900
        pid = 143, comm = mount_mfs

panic: trap
syncing disks... done

dumping to dev 8,1 offset 331363
dump 32 
unexpected machine check:

    mces    = 0x1
    vector  = 0x670
    param   = 0xfffffc0000006048
    pc      = 0xfffffc00004e6ea8
    ra      = 0xfffffc0000305ecc
    curproc = 0xfffffc0000663900
        pid = 143, comm = mount_mfs

panic: machine check

dumping to dev 8,1 offset 331363
dump device not ready

-- 
Kevin P. Neal                                http://www.pobox.com/~kpn/
           On the community of supercomputer fans:
"But what we lack in size we make up for in eccentricity." 
  from Steve Gombosi, comp.sys.super, 31 Jul 2000 11:22:43 -0600