diff -ur qemu/exec.c qemu-0.9.0/exec.c
--- qemu/exec.c	2007-02-06 00:01:54.000000000 +0100
+++ qemu-0.9.0/exec.c	2007-07-10 09:14:31.000000000 +0200
@@ -41,7 +41,7 @@
 //#define DEBUG_TB_INVALIDATE
 //#define DEBUG_FLUSH
 //#define DEBUG_TLB
-//#define DEBUG_UNASSIGNED
+#define DEBUG_UNASSIGNED
 
 /* make various TB consistency checks */
 //#define DEBUG_TB_CHECK 
@@ -1812,10 +1812,14 @@
     return p->phys_offset;
 }
 
+CPUState *__GLOBAL_env;
+
 static uint32_t unassigned_mem_readb(void *opaque, target_phys_addr_t addr)
 {
 #ifdef DEBUG_UNASSIGNED
     printf("Unassigned mem read  0x%08x\n", (int)addr);
+    cpu_dump_state(__GLOBAL_env, stdout, fprintf, 0);
+    abort();
 #endif
     return 0;
 }
@@ -1824,6 +1828,8 @@
 {
 #ifdef DEBUG_UNASSIGNED
     printf("Unassigned mem write 0x%08x = 0x%x\n", (int)addr, val);
+    cpu_dump_state(__GLOBAL_env, stdout, fprintf, 0);
+    abort();
 #endif
 }