amd64 on SU9400

I can netboot NetBSD-current/i386 on a system with a SU9400 which according
to http://ark.intel.com/Product.aspx?id=36697 has a 64-bit instruction set,
but not NetBSD-current/amd64.

Despite having NFS, DIAGNOSTIC, DEBUG, LOCKDEBUG, DDB, DDB_ONPANIC=1 in the
kernel, after "Loading nfs" and the /|\ animation the laptop simply reboots.

Any ideas given that works with i386?

Cheers,

Patrick