--- xnu/xnu-4570.71.2/iokit/Kernel/IOStartIOKit.cpp
+++ xnu/xnu-3789.31.2/iokit/Kernel/IOStartIOKit.cpp
@@ -77,7 +77,7 @@
 		IOService::resourceMatching("IONVRAM"), &t );
 #endif
 
-	clock_initialize_calendar();
+    clock_initialize_calendar();
 }
 
 void iokit_post_constructor_init(void)
@@ -111,6 +111,9 @@
 	obj->release();
     }
 }
+
+// From <osfmk/kern/debug.c>
+extern int debug_mode;
 
 /*****
  * Pointer into bootstrap KLD segment for functions never used past startup.
@@ -134,6 +137,10 @@
     // Compat for boot-args
     gIOKitTrace |= (gIOKitDebug & kIOTraceCompatBootArgs);
 	
+    // Check for the log synchronous bit set in io
+    if (gIOKitDebug & kIOLogSynchronous)
+        debug_mode = true;
+
     if( PE_parse_boot_argn( "pmtimeout", &debugFlags, sizeof (debugFlags) ))
         gCanSleepTimeout = debugFlags;
     //