Is there a known limitation of problem with Memory file system?

On an AS200-4/233 w/ 96M bytes main memory running the 0628 Snapshot, I 
have two swap partitions:  /dev/sd0b is ~ 750M bytes and /dev/sd1b is 
~250M bytes.  Both are listed as swap in /etc/fstab.  If I "mount -t mfs 
/dev/sd1b /tmp" it's fine, but if instead I try sd0b, the bigger one, I 
get:

fatal kernel trap:

    trap entry = 0x2 (memory management fault)
    a0         = 0x120176000
    a1         = 0x1
    a2         = 0xffffffffffffffff
    pc         = 0x120176000
    ra         = 0x120176000
    curproc    = 0xfffffe0000425800
        pid = 156, comm = mount_mfs

panic: trap
syncing disks... 7 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 giving up


I do have "/dev/sd1b /tmp mfs rw,noauto 0 0" in /etc/fstab, but the 
'noauto' should prevent that from interfering, shouldn't it?

I haven't yet got a dump because /var is smaller than main memory, and 
savecore apparently doesn't follow symlinks.  Before I pursue that, I may 
as well build a kernel with debug symbols.  Can anyone give me a quick 
clue on that?  Is it as simple as "config -g" and then copy the kernel, 
"strip -d" one copy and put that in / and keep the other copy for 
debugging?