diff -rubB sys-base/conf/options.i386 sys/conf/options.i386
--- sys-base/conf/options.i386	2008-01-16 22:46:18.000000000 +0100
+++ sys/conf/options.i386	2008-01-16 22:53:40.451948729 +0100
@@ -151,3 +151,6 @@
 
 # BPF just-in-time compiler
 BPF_JITTER		opt_bpf.h
+
+# Memory override options
+PHYSMEM_SIZE		opt_memory.h
diff -rubB sys-base/i386/i386/machdep.c sys/i386/i386/machdep.c
--- sys-base/i386/i386/machdep.c	2008-01-16 22:46:17.000000000 +0100
+++ sys/i386/i386/machdep.c	2008-01-17 23:21:52.608847487 +0100
@@ -49,6 +49,7 @@
 #include "opt_ipx.h"
 #include "opt_isa.h"
 #include "opt_kstack_pages.h"
+#include "opt_memory.h"
 #include "opt_maxmem.h"
 #include "opt_msgbuf.h"
 #include "opt_npx.h"
@@ -1676,6 +1677,12 @@
 	quad_t dcons_addr, dcons_size;
 
 	has_smap = 0;
+#ifdef PHYSMEM_SIZE
+	physmap[0] = 0;
+	physmap[1] = PHYSMEM_SIZE * 1024;
+	physmap_idx = 0;
+	goto physmap_done;
+#endif
 #ifdef XBOX
 	if (arch_i386_is_xbox) {
 		/*