diff --git a/src/harptool.cpp b/src/harptool.cpp
index e6bf4091..c3a61a37 100644
--- a/src/harptool.cpp
+++ b/src/harptool.cpp
@@ -207,13 +207,14 @@ int disasm_main(int argc, char **argv) {
 
 int emu_main(int argc, char **argv) {
   string archString("8w32/32/8/8"), imgFileName("a.out.bin");
-  bool showHelp, showStats;
+  bool showHelp, showStats, basicMachine;
 
   /* Read the command line arguments. */
   CommandLineArgFlag          fh("-h", "--help", "", showHelp);
   CommandLineArgSetter<string>fc("-c", "--core", "", imgFileName);
   CommandLineArgSetter<string>fa("-a", "--arch", "", archString);
   CommandLineArgFlag          fs("-s", "--stats", "", showStats);
+  CommandLineArgFlag          fb("-b", "--basic", "", basicMachine);
   
   CommandLineArg::readArgs(argc, argv);
 
@@ -235,7 +236,7 @@ int emu_main(int argc, char **argv) {
       return 1;
   }
 
-  MemoryUnit mu(4096, arch.getWordSize());
+  MemoryUnit mu(4096, arch.getWordSize(), basicMachine);
   Core core(arch, *dec, mu/*, ID in multicore implementations*/);
 
   RamMemDevice mem(imgFileName.c_str(), arch.getWordSize());
diff --git a/src/include/help.h b/src/include/help.h
index 52947572..1da55bff 100644
--- a/src/include/help.h
+++ b/src/include/help.h
@@ -17,7 +17,9 @@ namespace HarpTools {
       "  Display contextual help.\n",
       *emuHelp = "HARP Emulator command line arguments:\n"
                   "  -c, --core <filename>    RAM image\n"
-                  "  -a, --arch <arch string> Architecture string\n",
+                  "  -a, --arch <arch string> Architecture string\n"
+                  "  -s, --stats              Print stats on exit.\n"
+                  "  -b, --basic              Disable virtual memory.\n",
       *asmHelp = "HARP Assembler command line arguments:\n"
                   "  -a, --arch <arch string>\n"
                   "  -o, --output <filename>\n",
diff --git a/src/include/mem.h b/src/include/mem.h
index 7b93cb95..7ea8e5d0 100644
--- a/src/include/mem.h
+++ b/src/include/mem.h
@@ -106,10 +106,11 @@ namespace Harp {
 
   class MemoryUnit {
   public:
-    MemoryUnit(Size pageSize, Size addrBytes) : 
-      pageSize(pageSize), addrBytes(addrBytes), ad()
+    MemoryUnit(Size pageSize, Size addrBytes, bool disableVm = false) : 
+      pageSize(pageSize), addrBytes(addrBytes), ad(), disableVm(disableVm)
     {
-      tlb[0] = TLBEntry(0, 077);
+      if (!disableVm)
+        tlb[0] = TLBEntry(0, 077);
     }
     void attach(MemDevice &m, Addr base);
 
@@ -162,6 +163,8 @@ namespace Harp {
     TLBEntry tlbLookup(Addr vAddr, Word flagMask);
 
     Size pageSize, addrBytes;
+
+    bool disableVm;
   };
 };
 
diff --git a/src/mem.cpp b/src/mem.cpp
index f151aa98..18446d6b 100644
--- a/src/mem.cpp
+++ b/src/mem.cpp
@@ -80,6 +80,7 @@ Byte *MemoryUnit::ADecoder::getPtr(Addr a, Size sz, Size wordSize) {
   MemDevice &m(doLookup(a, bit));
   a &= (2<<bit)-1;
   if (a + sz <= m.size()) return m.base() + a;
+  return NULL;
 }
 
 Word MemoryUnit::ADecoder::read(Addr a, bool sup, Size wordSize) {
@@ -97,7 +98,7 @@ void MemoryUnit::ADecoder::write(Addr a, Word w, bool sup, Size wordSize) {
 }
 
 Byte *MemoryUnit::getPtr(Addr a, Size s) {
-  ad.getPtr(a, s, addrBytes*8);
+  return ad.getPtr(a, s, addrBytes*8);
 }
 
 void MemoryUnit::attach(MemDevice &m, Addr base) {
@@ -127,23 +128,40 @@ Addr MemoryUnit::virtToPhys(Addr vAddr) {
 #endif
 
 Word MemoryUnit::read(Addr vAddr, bool sup) {
-  Word flagMask = sup?8:1;
-  TLBEntry t = tlbLookup(vAddr, flagMask);
-  Addr pAddr = t.pfn*pageSize + vAddr%pageSize;
+  Addr pAddr;
+  if (disableVm) {
+    pAddr = vAddr;
+  } else {
+    Word flagMask = sup?8:1;
+    TLBEntry t = tlbLookup(vAddr, flagMask);
+    pAddr = t.pfn*pageSize + vAddr%pageSize;
+  }
   return ad.read(pAddr, sup, 8*addrBytes);
 }
 
 Word MemoryUnit::fetch(Addr vAddr, bool sup) {
-  Word flagMask = sup?32:4;
-  TLBEntry t = tlbLookup(vAddr, flagMask);
-  Addr pAddr = t.pfn*pageSize + vAddr%pageSize;
+  Addr pAddr;
+
+  if (disableVm) {
+    pAddr = vAddr;
+  } else {
+    Word flagMask = sup?32:4;
+    TLBEntry t = tlbLookup(vAddr, flagMask);
+    pAddr = t.pfn*pageSize + vAddr%pageSize;
+  }
   return ad.read(pAddr, sup, 8*addrBytes);
 }
 
 void MemoryUnit::write(Addr vAddr, Word w, bool sup) {
-  Word flagMask = sup?16:2;
-  TLBEntry t = tlbLookup(vAddr, flagMask);
-  Addr pAddr = t.pfn*pageSize + vAddr%pageSize;
+  Addr pAddr;
+
+  if (disableVm) {
+    pAddr = vAddr;
+  } else {
+    Word flagMask = sup?16:2;
+    TLBEntry t = tlbLookup(vAddr, flagMask);
+    pAddr = t.pfn*pageSize + vAddr%pageSize;
+  }
   ad.write(pAddr, w, sup, 8*addrBytes);
 }