NetBSD crashes on 4 GB Supermicro

[<marcotte%panix.com@localhost>]

I'm having a problem running a NetBSD domU on one particular type of
system.

        SuperMicro PDSMI+ motherboard
        4 GB RAM (about 3.5 MB usable)
        Xen 3.0.3-0 (non-PAE, of course)
        dom0: Linux 2.6.16.29

Normally NetBSD will crash immediately upon startup on these systems.
Linux domUs work just fine. NetBSD also works fine on other 4GB systems.

The only way I can get NetBSD to work on these is if I tell Xen to
limit the RAM usage to 3G or less on the command line (mem=3072m).

That last 512MB or so may not seem like much, but without PAE support,
I'm trying to make use of every last available MB.

I have no idea how to debug a domU. Any help would be appreciated.

Thanks.

----------

This is what Xen has to say about it:

(XEN) domain_crash_sync called from entry.S (ff150e49)
(XEN) Domain 1 (vcpu#0) crashed on cpu#1:
(XEN) ----[ Xen-3.0.3-0  x86_32  debug=n  Not tainted ]----
(XEN) CPU:    1
(XEN) EIP:    e019:[<c02b6ea9>]
(XEN) EFLAGS: 00000246   CONTEXT: guest
(XEN) eax: ffffffff   ebx: d097d003   ecx: d097d000   edx: 00000000
(XEN) esi: 0000005b   edi: c0455000   ebp: c0317bb4   esp: c0317b78
(XEN) cr0: 8005003b   cr4: 000026d0   cr3: d097c000   cr2: 00000000
(XEN) ds: e021   es: e021   fs: 0000   gs: 0000   ss: e021   cs: e019
(XEN) Guest stack trace from esp=c0317b78:
(XEN)    00000000 c02b6ea9 0001e019 00010046 c02b798c d097a154 d0973061 00000000
(XEN)    00000000 00000000 c0454000 00000005 c0450c10 c0450000 c0459000 00000000
(XEN)    c0100179 c0317bbc 0000e021 c01044bc c0104520 00000000 00000000 00000000
(XEN)    00000000 00000000 00000000 c02ec8a0 00000000 00000000 00000000 00000000
(XEN)    00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[many more lines of zeros]