diff --git a/makefile b/makefile
index 41261378fe..9729ca0246 100644
--- a/makefile
+++ b/makefile
@@ -4,6 +4,14 @@ bld = build
 src = src
 classpath = classpath
 
+arch = $(shell uname -m)
+ifeq ($(arch),i586)
+	arch = i386
+endif
+ifeq ($(arch),i686)
+	arch = i386
+endif
+
 cxx = g++
 cc = gcc
 vg = nice valgrind --leak-check=full --num-callers=32 --db-attach=yes \
@@ -27,6 +35,7 @@ test-cflags = -DDEBUG_MEMORY
 stress-cflags = -DDEBUG_MEMORY -DDEBUG_MEMORY_MAJOR
 
 cpp-objects = $(foreach x,$(1),$(patsubst $(2)/%.cpp,$(bld)/%.o,$(x)))
+assembly-objects = $(foreach x,$(1),$(patsubst $(2)/%.S,$(bld)/%.o,$(x)))
 
 stdcpp-sources = $(src)/stdc++.cpp
 stdcpp-objects = $(call cpp-objects,$(stdcpp-sources),$(src))
@@ -58,7 +67,21 @@ interpreter-sources = \
 	$(src)/vm.cpp \
 	$(src)/heap.cpp \
 	$(src)/main.cpp
-interpreter-objects = $(call cpp-objects,$(interpreter-sources),$(src))
+
+ifeq ($(arch),i386)
+	interpreter-assembly-sources = $(src)/cdecl.S
+endif
+ifeq ($(arch),x86_64)
+	interpreter-assembly-sources = $(src)/amd64.S
+endif
+
+interpreter-cpp-objects = \
+	$(call cpp-objects,$(interpreter-sources),$(src))
+interpreter-assembly-objects = \
+	$(call assembly-objects,$(interpreter-assembly-sources),$(src))
+interpreter-objects = \
+	$(interpreter-cpp-objects) \
+	$(interpreter-assembly-objects)
 interpreter-cflags = $(slow) $(cflags)
 
 generator-headers = \
@@ -138,7 +161,7 @@ stress-all: $(stress-executable)
 .PHONY: clean
 clean:
 	@echo "removing $(bld)"
-	rm -r $(bld)
+	rm -rf $(bld)
 
 gen-arg = $(shell echo $(1) | sed -e 's:$(bld)/type-\(.*\)\.cpp:\1:')
 $(generated-code): %.cpp: $(src)/types.def $(generator-executable)
@@ -159,7 +182,12 @@ $(stdcpp-objects): $(bld)/%.o: $(src)/%.cpp
 	@mkdir -p $(dir $(@))
 	$(cxx) $(stdcpp-cflags) -c $(<) -o $(@)
 
-$(interpreter-objects): $(bld)/%.o: $(src)/%.cpp $(interpreter-depends)
+$(interpreter-cpp-objects): $(bld)/%.o: $(src)/%.cpp $(interpreter-depends)
+	@echo "compiling $(@)"
+	@mkdir -p $(dir $(@))
+	$(cxx) $(interpreter-cflags) -c $(<) -o $(@)
+
+$(interpreter-assembly-objects): $(bld)/%.o: $(src)/%.S
 	@echo "compiling $(@)"
 	@mkdir -p $(dir $(@))
 	$(cxx) $(interpreter-cflags) -c $(<) -o $(@)
diff --git a/src/amd64.S b/src/amd64.S
new file mode 100644
index 0000000000..b97bc8c15d
--- /dev/null
+++ b/src/amd64.S
@@ -0,0 +1,107 @@
+#include "types.h"
+
+.text
+.globl amd64Call
+.type amd64Call, @function
+
+amd64Call:
+   pushq  %rbp
+
+   // %rdi aka  0(%rbp): function
+   // %rsi aka  8(%rbp): stack
+   // %rdx aka 16(%rbp): stackSize
+   // %rcx aka 24(%rbp): gprTable
+   //  %r8 aka 32(%rbp): sseTable
+   //  %r9 aka 40(%rbp): returnType
+
+   // save our argument registers so we can clobber them
+   pushq  %r9
+   pushq  %r8
+   pushq  %rcx
+   pushq  %rdx
+   pushq  %rsi
+   pushq  %rdi
+   
+   movq   %rsp,%rbp
+
+   // reserve space for arguments passed via memory
+   subq   %rdx,%rsp
+
+   // copy memory arguments into place
+   movq   $0,%rcx
+   jmp    test
+
+loop:
+   movq   %rcx,%rax
+   movq   %rcx,%rdx
+   addq   %rsp,%rdx
+   addq   8(%rbp),%rax
+	 movq	  (%rax),%rax
+   movq   %rax,(%rdx)
+   addq   $8,%rcx
+
+test:
+   cmpq   16(%rbp),%rcx
+   jb     loop
+   
+   // do we need to load the general-purpose registers?
+   cmpq   $0,24(%rbp)
+   je     sse
+
+   // yes, we do
+   movq   24(%rbp),%rax
+   movq   0(%rax),%rdi
+   movq   8(%rax),%rsi
+   movq   16(%rax),%rcx
+   movq   24(%rax),%rdx
+   movq   32(%rax),%r8
+   movq   40(%rax),%r9
+
+sse:
+   // do we need to load the SSE registers?
+   cmpq   $0,32(%rbp)
+   je     call
+
+   // yes, we do
+   movq   32(%rbp),%rax
+   movq   0(%rax),%xmm0
+   movq   8(%rax),%xmm1
+   movq   16(%rax),%xmm2
+   movq   24(%rax),%xmm3
+   movq   32(%rax),%xmm4
+   movq   40(%rax),%xmm5
+   movq   48(%rax),%xmm6
+   movq   64(%rax),%xmm7
+
+call:
+   call   *0(%rbp)
+   
+   // clear space reserved for memory arguments
+   movq   16(%rbp),%rcx
+   addq   %rcx,%rsp
+
+   // handle return value based on expected type
+   movq   40(%rbp),%rcx
+
+void:   
+   cmpq   $VOID_TYPE,%rcx
+   jne    float
+   jmp    exit
+   
+float:   
+   cmpq   $FLOAT_TYPE,%rcx
+   je     copy
+   cmpq   $DOUBLE_TYPE,%rcx
+   jne    exit
+   
+copy:
+   movq   %xmm0,%rax
+
+exit:
+   movq   %rbp,%rsp
+
+   // pop our argument registers
+   addq   $48,%rsp
+   
+   popq   %rbp
+   ret
diff --git a/src/cdecl.S b/src/cdecl.S
new file mode 100644
index 0000000000..4abdc9aa09
--- /dev/null
+++ b/src/cdecl.S
@@ -0,0 +1,78 @@
+#include "types.h"
+
+.text
+.globl cdeclCall
+.type cdeclCall, @function
+   
+cdeclCall:
+   pushl  %ebp
+   movl   %esp,%ebp
+
+   //  8(%ebp): function
+   // 12(%ebp): stack
+   // 16(%ebp): stackSize
+   // 20(%ebp): returnType
+   
+   // reserve space for arguments
+   movl   16(%ebp),%ecx
+   subl   %ecx,%esp
+
+   // copy arguments into place
+   movl   $0,%ecx
+   jmp    test
+
+loop:
+   movl   %ecx,%eax
+   movl   %ecx,%edx
+   addl   %esp,%edx
+   addl   12(%ebp),%eax
+	 movl	  (%eax),%eax
+   movl   %eax,(%edx)
+   addl   $4,%ecx
+
+test:
+   cmpl   16(%ebp),%ecx
+   jb     loop
+
+   // call function
+   call   *8(%ebp)
+
+   // clear space reserved for arguments
+   movl   16(%ebp),%ecx
+   addl   %ecx,%esp
+
+   // handle return value based on expected type
+   movl   20(%ebp),%ecx
+   
+void:   
+   cmpl   $VOID_TYPE,%ecx
+   jne    int64
+   jmp    exit
+
+int64: 
+   cmpl   $INT64_TYPE,%ecx
+   jne    float
+   jmp    exit
+   
+float:   
+   cmpl   $FLOAT_TYPE,%ecx
+   jne    double
+   fstps  8(%ebp)
+   movl   8(%ebp),%eax
+   jmp    int32
+
+double:
+   cmpl   $DOUBLE_TYPE,%ecx
+   jne    int32
+   fstpl  8(%ebp)
+   movl   8(%ebp),%eax
+   movl   12(%ebp),%edx
+   jmp    exit
+   
+int32:
+   movl   $0,%edx
+
+exit:
+   movl   %ebp,%esp
+   popl   %ebp
+   ret
diff --git a/src/common.h b/src/common.h
index 4b05fbbcfe..8e94fe7a61 100644
--- a/src/common.h
+++ b/src/common.h
@@ -6,6 +6,7 @@
 #include "stdarg.h"
 #include "string.h"
 #include "stdio.h"
+#include "types.h"
 
 #define NO_RETURN __attribute__((noreturn))
 
diff --git a/src/main.cpp b/src/main.cpp
index ffb14b3bd4..19294850b3 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -11,6 +11,77 @@
 
 using namespace vm;
 
+#ifdef __i386__
+
+extern "C" uint64_t
+cdeclCall(void* function, void* stack, unsigned stackSize,
+          unsigned returnType);
+
+namespace {
+
+inline uint64_t
+dynamicCall(void* function, uint32_t* arguments, uint8_t*,
+            unsigned, unsigned argumentsSize, unsigned returnType)
+{
+  return cdeclCall(function, arguments, argumentsSize, returnType);
+}
+
+} // namespace
+
+#elif defined __x86_64__
+
+extern "C" uint64_t
+amd64Call(void* function, void* stack, unsigned stackSize,
+          void* gprTable, void* sseTable, unsigned returnType);
+
+namespace {
+
+uint64_t
+dynamicCall(void* function, uint64_t* arguments, uint8_t* argumentTypes,
+            unsigned argumentCount, unsigned, unsigned returnType)
+{
+  const unsigned GprCount = 6;
+  uint64_t gprTable[GprCount];
+  unsigned gprIndex = 0;
+
+  const unsigned SseCount = 8;
+  uint64_t sseTable[SseCount];
+  unsigned sseIndex = 0;
+
+  uint64_t stack[argumentCount];
+  unsigned stackIndex = 0;
+
+  for (unsigned i = 0; i < argumentCount; ++i) {
+    switch (argumentTypes[i]) {
+    case FLOAT_TYPE:
+    case DOUBLE_TYPE: {
+      if (sseIndex < SseCount) {
+        sseTable[sseIndex++] = arguments[i];
+      } else {
+        stack[stackIndex++] = arguments[i];
+      }
+    } break;
+
+    default: {
+      if (gprIndex < GprCount) {
+        gprTable[gprIndex++] = arguments[i];
+      } else {
+        stack[stackIndex++] = arguments[i];
+      }
+    } break;
+    }
+  }
+
+  return amd64Call(function, stack, stackIndex * 8, (gprIndex ? gprTable : 0),
+                   (sseIndex ? sseTable : 0), returnType);
+}
+
+} // namespace
+
+#else
+#  error unsupported platform
+#endif
+
 namespace {
 
 const bool Verbose = false;
@@ -115,13 +186,10 @@ class System: public vm::System {
     return 0;
   }
 
-  virtual uint64_t call(void* ,//function,
-                        unsigned ,//argumentCount,
-                        uint32_t* ,//argumentTable,
-                        uint8_t* ,//argumentSizeTable,
-                        unsigned )//returnSize)
+  virtual uint64_t call(void* function, uintptr_t* arguments, uint8_t* types,
+                        unsigned count, unsigned size, unsigned returnType)
   {
-    ::abort();
+    return dynamicCall(function, arguments, types, count, size, returnType);
   }
 
   virtual Status load(vm::System::Library** lib,
diff --git a/src/system.h b/src/system.h
index cee0f8a285..edd1d48176 100644
--- a/src/system.h
+++ b/src/system.h
@@ -42,9 +42,9 @@ class System {
   virtual void free(const void*) = 0;
   virtual Status start(Thread*) = 0;
   virtual Status make(Monitor**) = 0;
-  virtual uint64_t call(void* function, unsigned argumentCount,
-                        uint32_t* argumentTable, uint8_t* argumentSizeTable,
-                        unsigned returnSize) = 0;
+  virtual uint64_t call(void* function, uintptr_t* arguments, uint8_t* types,
+                        unsigned count, unsigned size,
+                        unsigned returnType) = 0;
   virtual Status load(Library**, const char* name, Library* next) = 0;
   virtual void abort() = 0;
 
diff --git a/src/types.def b/src/types.def
index cb2ef259a2..645a984e58 100644
--- a/src/types.def
+++ b/src/types.def
@@ -37,7 +37,7 @@
   (uint16_t argumentTableSize)
   (uint8_t returnCode)
   (uint8_t builtin)
-  (array uint8_t parameterCodes))
+  (array uint8_t parameterTypes))
 
 (type pointer
   (void* value))
diff --git a/src/types.h b/src/types.h
new file mode 100644
index 0000000000..dd3e09f8a2
--- /dev/null
+++ b/src/types.h
@@ -0,0 +1,13 @@
+#ifndef TYPES_H
+#define TYPES_H
+
+#define VOID_TYPE 0
+#define INT8_TYPE 1
+#define INT16_TYPE 2
+#define INT32_TYPE 3
+#define INT64_TYPE 4
+#define FLOAT_TYPE 5
+#define DOUBLE_TYPE 6
+#define POINTER_TYPE 7
+
+#endif//TYPES_H
diff --git a/src/vm.cpp b/src/vm.cpp
index 6ac710d5ec..b53bd7cac7 100644
--- a/src/vm.cpp
+++ b/src/vm.cpp
@@ -17,7 +17,8 @@ using namespace vm;
 
 namespace {
 
-static const bool Debug = true;
+static const bool Verbose = false;
+static const bool Debug = false;
 
 class Thread;
 
@@ -827,7 +828,7 @@ makeRuntimeException(Thread* t, object message)
 {
   PROTECT(t, message);
   object trace = makeTrace(t);
-  return makeClassCastException(t, message, trace, 0);
+  return makeRuntimeException(t, message, trace, 0);
 }
 
 object
@@ -935,6 +936,33 @@ fieldCode(Thread* t, unsigned javaCode)
   }
 }
 
+unsigned
+fieldType(Thread* t, unsigned code)
+{
+  switch (code) {
+  case VoidField:
+    return VOID_TYPE;
+  case ByteField:
+  case BooleanField:
+    return INT8_TYPE;
+  case CharField:
+  case ShortField:
+    return INT16_TYPE;
+  case DoubleField:
+    return DOUBLE_TYPE;
+  case FloatField:
+    return FLOAT_TYPE;
+  case IntField:
+    return INT32_TYPE;
+  case LongField:
+    return INT64_TYPE;
+  case ObjectField:
+    return POINTER_TYPE;
+
+  default: abort(t);
+  }
+}
+
 uint64_t
 primitiveValue(Thread* t, unsigned code, object o)
 {
@@ -1828,15 +1856,19 @@ resolveClass(Thread* t, object spec)
       (reinterpret_cast<const char*>(&byteArrayBody(t, spec, 0)));
 
     if (data) {
-      fprintf(stderr, "parsing %s\n", &byteArrayBody
-              (t, spec, 0));
+      if (Verbose) {
+        fprintf(stderr, "parsing %s\n", &byteArrayBody
+                (t, spec, 0));
+      }
 
       // parse class file
       class_ = parseClass(t, data->start(), data->length());
       data->dispose();
 
-      fprintf(stderr, "done parsing %s\n", &byteArrayBody
-              (t, className(t, class_), 0));
+      if (Verbose) {
+        fprintf(stderr, "done parsing %s\n", &byteArrayBody
+                (t, className(t, class_), 0));
+      }
 
       PROTECT(t, class_);
 
@@ -1929,15 +1961,17 @@ makeNativeMethodData(Thread* t, object method, void* function, bool builtin)
                                      0, // argument table size
                                      0, // return code,
                                      builtin,
-                                     methodParameterCount(t, method),
+                                     methodParameterCount(t, method) + 1,
                                      false);
         
-  unsigned argumentTableSize = BytesPerWord / 4;
+  unsigned argumentTableSize = BytesPerWord;
   unsigned index = 0;
 
+  nativeMethodDataParameterTypes(t, data, index++) = POINTER_TYPE;
+
   if ((methodFlags(t, method) & ACC_STATIC) == 0) {
-    nativeMethodDataParameterCodes(t, data, index++) = ObjectField;
-    argumentTableSize += BytesPerWord / 4;
+    nativeMethodDataParameterTypes(t, data, index++) = POINTER_TYPE;
+    argumentTableSize += BytesPerWord;
   }
 
   const char* s = reinterpret_cast<const char*>
@@ -1945,22 +1979,22 @@ makeNativeMethodData(Thread* t, object method, void* function, bool builtin)
   ++ s; // skip '('
   while (*s and *s != ')') {
     unsigned code = fieldCode(t, *s);
-    nativeMethodDataParameterCodes(t, data, index++) = code;
+    nativeMethodDataParameterTypes(t, data, index++) = fieldType(t, code);
 
     switch (*s) {
     case 'L':
-      argumentTableSize += BytesPerWord / 4;
+      argumentTableSize += BytesPerWord;
       while (*s and *s != ';') ++ s;
       ++ s;
       break;
 
     case '[':
-      argumentTableSize += BytesPerWord / 4;
+      argumentTableSize += BytesPerWord;
       while (*s == '[') ++ s;
       break;
       
     default:
-      argumentTableSize += divide(primitiveSize(t, code), 4);
+      argumentTableSize += pad(primitiveSize(t, code));
       ++ s;
       break;
     }
@@ -2020,44 +2054,50 @@ invokeNative(Thread* t, object method)
     return 0;
   }
 
-  unsigned parameterCount = methodParameterCount(t, method);
+  unsigned count = methodParameterCount(t, method);
 
-  uint32_t args[nativeMethodDataArgumentTableSize(t, data)];
-  uint8_t sizes[parameterCount + 1];
+  unsigned size = nativeMethodDataArgumentTableSize(t, data);
+  uintptr_t args[size / BytesPerWord];
   unsigned offset = 0;
 
-  sizes[0] = BytesPerWord;
-  memcpy(args + offset, &t, BytesPerWord);
-  offset += BytesPerWord / 4;
+  args[offset++] = reinterpret_cast<uintptr_t>(t);
 
-  for (unsigned i = 0; i < parameterCount; ++i) {
-    unsigned code = nativeMethodDataParameterCodes(t, data, i);
+  for (unsigned i = 0; i < count; ++i) {
+    unsigned type = nativeMethodDataParameterTypes(t, data, i);
+    unsigned position = (t->sp - count) + i;
+    object o = t->stack[position];
 
-    if (code == ObjectField) {
-      sizes[i + 1] = BytesPerWord;
-      unsigned position = (t->sp - parameterCount) + i;
-      if (t->stack[position]) {
-        memcpy(args + offset, t->stack + position, BytesPerWord);
-      } else {
-        memset(args + offset, 0, BytesPerWord);
-      }
-      offset += BytesPerWord / 4;
-    } else {
-      sizes[i + 1] = primitiveSize(t, code);
-      uint64_t v = primitiveValue(t, code, t->stack[t->sp + i]);
-      if (sizes[i + 1] == 8) {
-        memcpy(args + offset, &v, 8);
-        offset += 2;
-      } else {
-        args[offset++] = v;
-      }
+    switch (type) {
+    case INT8_TYPE:
+      args[offset++] = cast<uint8_t>(o, BytesPerWord);
+      break;
+
+    case INT16_TYPE:
+      args[offset++] = cast<uint16_t>(o, BytesPerWord);
+      break;
+
+    case INT32_TYPE:
+    case FLOAT_TYPE:
+      args[offset++] = cast<uint32_t>(o, BytesPerWord);
+      break;
+
+    case INT64_TYPE:
+    case DOUBLE_TYPE: {
+      uint64_t v = cast<uint64_t>(o, BytesPerWord);
+      memcpy(args + offset, &v, 8);
+      offset += (8 / BytesPerWord);
+    } break;
+
+    case POINTER_TYPE:
+      args[offset++] = reinterpret_cast<uintptr_t>(t->stack + position);
+      break;
+
+    default: abort(t);
     }
   }
 
   unsigned returnCode = nativeMethodDataReturnCode(t, data);
-  unsigned returnSize
-    = (returnCode == ObjectField ? 4 : primitiveSize(t, returnCode));
-
+  unsigned returnType = fieldType(t, returnCode);
   void* function = nativeMethodDataFunction(t, data);
 
   bool builtin = nativeMethodDataBuiltin(t, data);
@@ -2065,11 +2105,13 @@ invokeNative(Thread* t, object method)
     enter(t, Thread::IdleState);
   }
 
-  uint64_t rv = t->vm->system->call(function,
-                                    parameterCount,
-                                    args,
-                                    sizes,
-                                    returnSize);
+  uint64_t rv = t->vm->system->call
+    (function,
+     args,
+     &nativeMethodDataParameterTypes(t, data, 0),
+     count + 1,
+     size,
+     returnType);
 
   if (not builtin) {
     enter(t, Thread::ActiveState);
@@ -3656,6 +3698,8 @@ run(Thread* t)
       if (nativeMethodDataReturnCode(t, methodCode(t, code)) != VoidField) {
         push(t, r);
       }
+
+      code = methodCode(t, frameMethod(t, frame));
     } else {
       if (UNLIKELY(codeMaxStack(t, methodCode(t, code)) + base
                    > Thread::StackSizeInWords))
@@ -3734,7 +3778,7 @@ run(Thread* t)
     }
 
     for (; p; p = traceNext(t, p)) {
-      fprintf(stderr, "  at %s:%s\n",
+      fprintf(stderr, "  at %s.%s\n",
               &byteArrayBody
               (t, className(t, methodClass(t, traceMethod(t, p))), 0),
               &byteArrayBody