Index: /usr/src/sys/powerpc/powerpc/mp_machdep.c
===================================================================
--- /usr/src/sys/powerpc/powerpc/mp_machdep.c   (revision 345758)
+++ /usr/src/sys/powerpc/powerpc/mp_machdep.c   (working copy)
@@ -77,9 +77,14 @@
        PCPU_SET(awake, 1);
        __asm __volatile("msync; isync");
 
+       powerpc_sync();
        while (ap_letgo == 0)
+       {
                __asm __volatile("or 31,31,31");
+               powerpc_sync();
+       }
        __asm __volatile("or 6,6,6");
+       isync();
 
        /*
         * Set timebase as soon as possible to meet an implicit rendezvous
@@ -262,8 +267,11 @@
        __asm __volatile("msync; isync");
        
        /* Let APs continue */
-       atomic_store_rel_int(&ap_letgo, 1);
+       ap_letgo= 1;    // depend on prior sync, no need to lwsync first
 
+       powerpc_sync(); // analogous to what the ap's do (more similar time frame?)
+       if (ap_letgo) isync();
+
        platform_smp_timebase_sync(ap_timebase, 0);
 
        while (ap_awake < smp_cpus)