size = dir_size,
                                                     use_map = options.use_map,
                                                     map_levels = \
-                                                    options.map_levels),
+                                                    options.map_levels,
+                                                    numa_high_bit = \
+                                                      options.numa_high_bit),
                                          probeFilter = pf,
                                          memBuffer = mem_cntrl,
                                          probe_filter_enabled = options.pf_on,
 
                       help="'fixed'|'flexible'")
 
     # ruby mapping options
-    parser.add_option("--numa-high-bit", type="int", default=None,
+    parser.add_option("--numa-high-bit", type="int", default=0,
                       help="high order address bit to use for numa mapping. " \
                            "0 = highest bit, not specified = lowest bit")
 
 
     m_num_entries = m_size_bytes / RubySystem::getBlockSizeBytes();
 
     if (m_use_map) {
-        int entry_bits = floorLog2(m_num_entries);
-        assert(entry_bits >= m_map_levels);
-        m_sparseMemory = new SparseMemory(entry_bits, m_map_levels);
+        m_sparseMemory = new SparseMemory(m_map_levels);
     } else {
         m_entries = new Directory_Entry*[m_num_entries];
         for (int i = 0; i < m_num_entries; i++)
 
     size = Param.MemorySize("1GB", "capacity in bytes")
     use_map = Param.Bool(False, "enable sparse memory")
     map_levels = Param.Int(4, "sparse memory map levels")
-    numa_high_bit = Param.Int(0, "numa high bit")
+    # the default value of the numa high bit is specified in the command line
+    # option and must be passed into the directory memory sim object
+    numa_high_bit = Param.Int("numa high bit")
 
  */
 
 #include "mem/ruby/system/SparseMemory.hh"
+#include "mem/ruby/system/System.hh"
 
 using namespace std;
 
-SparseMemory::SparseMemory(int number_of_bits, int number_of_levels)
+SparseMemory::SparseMemory(int number_of_levels)
 {
     int even_level_bits;
     int extra;
-    m_total_number_of_bits = number_of_bits;
+    m_total_number_of_bits = RubySystem::getMemorySizeBits() 
+        - RubySystem::getBlockSizeBits();;
+
     m_number_of_levels = number_of_levels;
 
     //
 
 class SparseMemory
 {
   public:
-    SparseMemory(int number_of_bits, int number_of_levels);
+    SparseMemory(int number_of_levels);
     ~SparseMemory();
 
     void printConfig(std::ostream& out) { }