In case you haven't been following the tech@ list...BIGMEM is now on by default in the amd64 April 4th snapshot:
Code:
OpenBSD 4.9-current (GENERIC.MP) #865: Mon Apr 4 13:03:14 MDT 2011
deraadt@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
real mem = 137428045824 (131061MB)
avail mem = 133755703296 (127559MB)
mainbus0 at root
bios0 at mainbus0: SMBIOS rev. 2.6 @ 0xdf79c000 (103 entries)
bios0: vendor Dell Inc. version "1.1.9" date 05/21/2010
bios0: Dell Inc. PowerEdge R715