diff -r 1c93580f459b -r 09e9c7c3113d configs/common/Simulation.py
--- a/configs/common/Simulation.py	Fri Jan 13 06:23:54 2012 -0600
+++ b/configs/common/Simulation.py	Fri Jan 13 06:55:34 2012 -0600
@@ -43,7 +43,7 @@
     if options.cpu_type == "timing":
         class TmpClass(TimingSimpleCPU): pass
     elif options.cpu_type == "detailed":
-        if not options.caches:
+        if not options.caches and not options.ruby:
             print "O3 CPU must be used with caches"
             sys.exit(1)
         class TmpClass(DerivO3CPU): pass
diff -r 1c93580f459b -r 09e9c7c3113d configs/example/ruby_fs.py
--- a/configs/example/ruby_fs.py	Fri Jan 13 06:23:54 2012 -0600
+++ b/configs/example/ruby_fs.py	Fri Jan 13 06:55:34 2012 -0600
@@ -82,6 +82,7 @@
 execfile(os.path.join(config_root, "common", "Options.py"))
 
 (options, args) = parser.parse_args()
+options.ruby = True
 
 if args:
     print "Error: script doesn't take any positional arguments"
@@ -105,9 +106,13 @@
 # fast forward with the atomic cpu and instead set the FutureClass to None.
 # Therefore the cpus resolve to the correct names and unserialize correctly.
 #
-class CPUClass(TimingSimpleCPU): pass
-test_mem_mode = 'timing'
-FutureClass = None
+
+# system under test can be any CPU
+if not (options.cpu_type == "detailed" or
+        options.cpu_type == "timing"):
+    print >> sys.stderr, "Ruby works with TimingSimpleCPU or O3CPU!!"
+    sys.exit(1)
+(CPUClass, test_mem_mode, FutureClass) = Simulation.setCPUClass(options)
 
 CPUClass.clock = options.clock
 
diff -r 1c93580f459b -r 09e9c7c3113d configs/example/se.py
--- a/configs/example/se.py	Fri Jan 13 06:23:54 2012 -0600
+++ b/configs/example/se.py	Fri Jan 13 06:55:34 2012 -0600
@@ -154,17 +154,11 @@
     numThreads = len(workloads)
     
 if options.ruby:
-    if options.cpu_type == "detailed":
-        print >> sys.stderr, "Ruby only works with TimingSimpleCPU!!"
+    if not (options.cpu_type == "detailed" or
+            options.cpu_type == "timing"):
+        print >> sys.stderr, "Ruby works with TimingSimpleCPU or O3CPU!!"
         sys.exit(1)
-    elif not options.cpu_type == "timing":
-        print >> sys.stderr, "****WARN:  using Timing CPU since it's needed by Ruby"
-
-    class CPUClass(TimingSimpleCPU): pass
-    test_mem_mode = 'timing'
-    FutureClass = None
-else:
-    (CPUClass, test_mem_mode, FutureClass) = Simulation.setCPUClass(options)
+(CPUClass, test_mem_mode, FutureClass) = Simulation.setCPUClass(options)
 
 CPUClass.clock = '2GHz'
 CPUClass.numThreads = numThreads;