shutdown drops into db{0} on Digital PC 3000

[Ray Phillips <r.phillips%uq.edu.au@localhost>]

I've installed NetBSD/i386 6.0.1 on a DEC Digital PC 3000 which says 
this during POST:

Phoenix BIOS 4.0 Release 6.0

DIGITAL PC 3500 Version 1.08
Copyright (C) 1998 Digital Equipment Corporation
All Right Reserved

CPU = Pentium II 266 MHz
0000640K System RAM Passed
0062464K Extended RAM Passed


It shows no signs of instability when running, for example it builds 
6.0.1 from source in ~ 48 hours, but when a shutdown command is 
executed it drops into db{0} and reboots:


tt7# shutdown -h now
Shutdown NOW!
shutdown: [pid 41]
tt7# wall: You have write permission turned off; no reply possible

*** FINAL System shutdown message from root@tt7 ***
System going down IMMEDIATELY


Mar 17 02:21:15 tt7 shutdown: halt by root:

System shutdown time has arrived

About to run shutdown hooks...
Stopping cron.
Stopping inetd.
Saved entropy to disk.
Removing block-type swap devices
swapctl: removing /dev/wd0b as swap device
Sun Mar 17 02:21:18 EST 2013

Done running shutdown hooks.
Mar 17 02:21:23 tt7 syslogd[347]: Exiting on signal 15
syncing disks... done
cd0: detached
sysbeep0: detached
midi0: detached
atapibus0: detached
npx0: detached
pcppi0: detached
atabus1: detached
pci1: detached
uvm_fault(0xc1446948, 0, 1) -> 0xe
fatal page fault in supervisor mode
trap type 6 code 0 eip c0558023 cs 8 eflags 10292 cr2 0 ilevel 0
Skipping crash dump on recursive panic
panic: trap
cpu0: Begin traceback...
printf_nolog(c0ba9fab,caf6ba64,caf6ba64,c0558023,8,10292,0,0,c079146d,a) 
at netbsd:printf_nolog
trap_tss() at netbsd:trap_tss
--- trap via task gate ---
4:
cpu0: End traceback...
                      rebooting...



Choosing sysinst's "Halt the system" command after booting from the 
install CD drops into db{0} and waits for input:


 NetBSD/i386 6.0.1

 This menu-driven tool is designed to help you install NetBSD to a hard disk,
 or upgrade an existing NetBSD system, with a minimum of work.
 In the following menus type the reference letter (a, b, c, ...) to select an
 item, or type CTRL+N/CTRL+P to select the next/previous item.
 The arrow keys and Page-up/Page-down may also work.
 Activate the current selection from the menu by typing the enter key.

 Thank you for using NetBSD!

                         .............................
                         . NetBSD-6.0.1 Utilities    .
                         .                           .
                         . a: Run /bin/sh            .
                         . b: Set timezone           .
                         . c: Configure network      .
                         . d: Logging functions      .
                         .>e: Halt the system        .
                         . x: Back to main menu      .
                         .............................

syncing disks... done
cd0: detached
sysbeep0: detached
midi0: detached
atapibus0: detached
wd0: detached
npx0: detached
pcppi0: detached
atabus1: detached
atabus0: detached
pci1: detached
uvm_fault(0xc1452bd0, 0, 1) -> 0xe
fatal page fault in supervisor mode
trap type 6 code 0 eip c0558023 cs 8 eflags 10292 cr2 0 ilevel 0
kernel: supervisor trap page fault, code=0
Stopped in pid 46.1 (halt) at   netbsd:callout_halt+0x11:       movl 
0(%ebx),
%esi
db{0}>


Is this likely to be caused by something in the system's firware, or 
perhaps faulty RAM?  Does anyone know if a newer version of the BIOS 
is available?

This is the only DEC PC I've installed NetBSD onto, so don't know if 
this behaviour is typical of them.

The only other one I've tried to install it on is a Digital PC 5000, 
a Pentium I machine, which crashes when loading the install CD's 
kernel.  (Curiously, the number on the front of the P I box is 5000 
but 3000 on the front of the more recent P II machine.)


Ray