diff -r 83e491dac016 -r bd07589f5907 configs/example/fs.py
--- a/configs/example/fs.py	Thu Nov 01 13:02:20 2012 +0000
+++ b/configs/example/fs.py	Thu Nov 01 16:10:57 2012 +0000
@@ -117,13 +117,19 @@
 
 test_sys.cpu = [TestCPUClass(cpu_id=i) for i in xrange(np)]
 
+# Determine the memory ranges of the test system so they can be used
+# by the I/O cache or bridge to determine what ranges are visible to
+# the masters connected to the I/O bus.
+test_sys_mem_ranges = map(lambda mem: mem.range,
+                          test_sys.memories.unproxy(test_sys))
+
 if options.caches or options.l2cache:
     test_sys.iocache = IOCache(clock = '1GHz',
-                               addr_ranges=[test_sys.physmem.range])
+                               addr_ranges = test_sys_mem_ranges)
     test_sys.iocache.cpu_side = test_sys.iobus.master
     test_sys.iocache.mem_side = test_sys.membus.slave
 else:
-    test_sys.iobridge = Bridge(delay='50ns', ranges = [test_sys.physmem.range])
+    test_sys.iobridge = Bridge(delay='50ns', ranges = test_sys_mem_ranges)
     test_sys.iobridge.slave = test_sys.iobus.master
     test_sys.iobridge.master = test_sys.membus.slave
 
@@ -161,8 +167,15 @@
         drive_sys.cpu.fastmem = True
     if options.kernel is not None:
         drive_sys.kernel = binary(options.kernel)
+
+    # Determine the memory ranges of the drive system so they can be
+    # used by the I/O bridge to determine what ranges are visible to
+    # the masters connected to the I/O bus.
+    drive_sys_mem_ranges = map(lambda mem: mem.range,
+                               drive_sys.memories.unproxy(drive_sys))
+
     drive_sys.iobridge = Bridge(delay='50ns',
-                                ranges = [drive_sys.physmem.range])
+                                ranges = drive_sys_mem_ranges)
     drive_sys.iobridge.slave = drive_sys.iobus.master
     drive_sys.iobridge.master = drive_sys.membus.slave