diff -r b1ddaf4e6499 -r 7bdd3e65c938 src/mem/simple_dram.cc
--- a/src/mem/simple_dram.cc	Fri Jul 12 10:48:57 2013 +0100
+++ b/src/mem/simple_dram.cc	Fri Jul 12 10:48:58 2013 +0100
@@ -851,6 +851,10 @@
 
     DPRINTF(DRAM, "Activate at tick %d\n", act_tick);
 
+    // if the activation limit is disabled then we are done
+    if (actTicks.empty())
+        return;
+
     // sanity check
     if (actTicks.back() && (act_tick - actTicks.back()) < tXAW) {
         panic("Got %d activates in window %d (%d - %d) which is smaller "