diff --git a/README b/README
index 947da49..a35f7cc 100644
--- a/README
+++ b/README
@@ -2,4 +2,8 @@ This project's goal is to fully emulate the 65816 microprocessor in JavaScript.
 
 After achieving that goal the next step will be to create a new branch that will focus on emulating the SNES.  Any CPU related improvements that aren't specific to the SNES will be merged back.
 
-You call the execute function of the cpu object with a raw hex string representing the program you wish to emulate and it will execute those instructions as close to the 65816 as possible.
+Here is a short example of how to use the emulator:
+
+var cpu = new CPU_65816();
+cpu.load_binary("18fba9ff", 0x8000); // Load the program at 0x8000 in memory
+cpu.execute(0x8000);                 // Execute starting at 0x8000
diff --git a/cpu.js b/cpu.js
index 171f7bd..c2bd874 100755
--- a/cpu.js
+++ b/cpu.js
@@ -255,28 +255,23 @@ function CPU_65816() {
   /**
    * Load given program into memory and prepare for execution.
    */ 
-  this.load_program = function(raw_hex, has_header) {
-    this.mmu.load_rom(raw_hex);
-    this.r.pc = 0x8000;
-
-    // Skip the header(the first 512 bytes) if there is one present for now.
-    if(has_header) {
-      this.r.pc += 4096;
-    }
+  this.load_binary = function(raw_hex, memory_location_start) {
+    var loc = memory_location_start;
+    var byte_buffer = [];
+    for(var i = 0; i < raw_hex.length; i++) {
+      byte_buffer.push(raw_hex[i]);
+      if(byte_buffer.length===2) {
+        this.mmu.store_byte(loc, parseInt(byte_buffer[0]+byte_buffer[1],
+                                          "16"));
+        loc++;
+        byte_buffer = [];      
+      } 
+    } 
   };
 
   /**
-   * Take a raw hex string representing the program and execute it.
-   */
-  this.execute = function(raw_hex, has_header) {
-    this.load_program(raw_hex, has_header);
-    this.start(); 
-  };
-  
-  /**
-   * Step through the processing of a single byte from the current location of
-   * the program counter.
-   * TODO: Refactor the code to only process a single byte per step call
+   * Step through the processing of a single instruction from the current
+   * location of the program counter.
    */  
   this.step = function() {
     if(this.interrupt&&(!this.p.i|(this.interrupt===this.INTERRUPT.NMI))) {
@@ -364,11 +359,6 @@ function CPU_65816() {
       return;
     }
     var operation = this.opcode_map[b];
-    // Check if unsupported opcode.
-    if(operation==null) {
-      this.executing = false;
-      return;
-    }
     var bytes_required = operation.bytes_required(this);
     if(bytes_required===1) {
       operation.execute(this);
@@ -385,7 +375,12 @@ function CPU_65816() {
       this.executing = false;
   };
 
-  this.start = function() {
+  /**
+   * TODO: Add ability for this function to limit number of cpu cycles per
+   * second.
+   */
+  this.execute = function(start_address) {
+    this.r.pc = start_address;
     this.executing = true;
     while(this.executing) {
        this.step();
@@ -493,19 +488,6 @@ function MMU() {
     } 
     this.memory[bank][location] = b;
   };
-
-  this.load_rom = function(raw_hex) {
-    var loc = 0x8000;
-    var byte_buffer = [];
-    for(var i = 0; i < raw_hex.length; i++) {
-      byte_buffer.push(raw_hex[i]);
-      if(byte_buffer.length===2) {
-        this.store_byte(loc, parseInt(byte_buffer[0]+byte_buffer[1], "16")); 
-        loc++;
-        byte_buffer = [];      
-      } 
-    }    
-  };
 }
 
 var STP = {
diff --git a/test/tests.js b/test/tests.js
index c36df64..153dc4a 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -33,7 +33,8 @@ function test_lda() {
   test("Make sure LDA with a constant properly loads an 8-bit value in "+
        "8-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9ff");
+    cpu.load_binary("18fba9ff", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xff, "The accumulator should be 0xff when 0xff is "+
                           "given as its argument in 8-bit "+
                           "memory/accumulator mode.");
@@ -45,7 +46,8 @@ function test_lda() {
   test("Make sure LDA with a constant properly loads a 16-bit value in "+
        "16-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9ffff");
+    cpu.load_binary("18fbc220a9ffff", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xffff, "The accumulator should be 0xffff when 0xffff is "+
                             "given as its argument in 16-bit "+
                             "memory/accumulator mode.");
@@ -58,7 +60,8 @@ function test_lda() {
   test("Make sure LDA with a direct page address loads an 8-bit value in "+
        "8-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba90185fea5fe"); 
+    cpu.load_binary("18fba90185fea5fe", 0x8000); 
+    cpu.execute(0x8000);
     equals(cpu.r.a, 1, "The accumulator should be 1 when 1 is "+
                        "loaded from $fe(direct page) in 8-bit "+
                        "memory/accumulator mode.");
@@ -70,7 +73,8 @@ function test_lda() {
   test("Make sure LDA with a direct page address loads a 16-bit value in "+
        "16-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a901ff85fea5fe");
+    cpu.load_binary("18fbc220a901ff85fea5fe", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xff01, "The accumulator should be 0xff01 when 0xff01 "+
                             "is loaded from $fe(direct page) in 16-bit "+
                             "memory/accumulator mode.");
@@ -82,7 +86,8 @@ function test_lda() {
   test("Make sure LDA with an absolute address loads an 8-bit value in "+
        "8-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9fe8dff0aa900adff0a");
+    cpu.load_binary("18fba9fe8dff0aa900adff0a", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfe, "The accumulator should be 0xfe when 0xfe is "+
                           "loaded from $0aff(absolute) in 8-bit "+
                           "memory/accumulator mode.");
@@ -94,7 +99,8 @@ function test_lda() {
   test("Make sure LDA with an absolute address loads a 16-bit value in "+
        "16-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9ffff8dff0aa90000adff0a");
+    cpu.load_binary("18fbc220a9ffff8dff0aa90000adff0a", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xffff, "The accumulator should be 0xffff when 0xffff "+
                             "is loaded from $0aff and $0b00(absolute) in 16-bit "+
                             "memory/accumulator mode.");
@@ -107,7 +113,8 @@ function test_lda() {
        "register loads an 8-bit value in 8-bit memory/accumulator mode.",
        function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba201a9ff85ffa900b5fe");
+    cpu.load_binary("18fba201a9ff85ffa900b5fe", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xff, "The accumulator should be 0xff when 0xff "+
                           "is loaded from direct page address $fe indexed "+
                           "with x(which is 1) and thus loaded from $ff in "+
@@ -124,7 +131,8 @@ function test_lda() {
        "register loads a 16-bit value in 16-bit memory/accumulator mode.",
        function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a201a9ffff85fea90000bdfd");
+    cpu.load_binary("18fbc220a201a9ffff85fea90000bdfd", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xffff, "The accumulator should be 0xffff when 0xffff "+
                             "is loaded from direct page addresses $fe and "+
                             "$ff after $fd is indexed with the x register("+
@@ -140,7 +148,8 @@ function test_lda() {
   test("Make sure LDA indirect given a direct page address loads an 8-bit "+
        "value in 8-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9ff85fea90a85ffa9068dff0aa900b2fe");
+    cpu.load_binary("18fba9ff85fea90a85ffa9068dff0aa900b2fe", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 6, "The accumulator should be 6 when LDA loads an 8-bit "+
                        "value using an indirect address in 8-bit mode "+
                        "memory/accumulator mode.");
@@ -152,7 +161,8 @@ function test_lda() {
   test("Make sure LDA indirect given a direct page address loads a 16-bit "+
        "value in 16-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9ff0a85fea9ffff8dff0aa90000b2fe");
+    cpu.load_binary("18fbc220a9ff0a85fea9ffff8dff0aa90000b2fe", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xffff, "The accumulator should be 0xffff when LDA loads "+
                             "a 16-bit value using an indirect address "+
                             "loaded from a direct page address.");
@@ -164,7 +174,8 @@ function test_lda() {
   test("Ensure that LDA absolute indexed by the x register works for 8-bit "+
        "memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9fa8dff0aa201a900bdfe0a");
+    cpu.load_binary("18fba9fa8dff0aa201a900bdfe0a", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfa, "The accumulator should be 0xfa when LDA loads "+
                           "an 8-bit value using absolute indexed x mode "+
                           "from $0aff");
@@ -178,7 +189,8 @@ function test_lda() {
   test("Ensure that LDA absolute indexed by the x register works for 16-bit "+
        "memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9fefa8dff0aa203bdfc0a");
+    cpu.load_binary("18fbc220a9fefa8dff0aa203bdfc0a", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfafe, "The accumulator should be 0xfafe when LDA "+
                             "loads a 16-bit value from $0aff using "+
                             "absolute indexed x addressing mode.");
@@ -192,7 +204,8 @@ function test_lda() {
   test("Ensure that LDA absolute indexed by the y register works for 8-bit "+
        "memory/acccumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9fe8dff0aa002a900b9fd0a");
+    cpu.load_binary("18fba9fe8dff0aa002a900b9fd0a", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfe, "The accumulator should be 0xfe when LDA loads an "+
                           "8-bit value from $0aff using absolute indexed y "+
                           "addressing mode."); 
@@ -206,7 +219,8 @@ function test_lda() {
   test("Ensure that LDA absolute indexed by the y register works for 16-bit "+
        "memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9fefa8dff0aa003a90000b9fc0a");
+    cpu.load_binary("18fbc220a9fefa8dff0aa003a90000b9fc0a", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfafe, "The accumulator should be 0xfafe when LDA loads "+
                             "a 16-bit value from $0aff using absolute "+
                             "indexed y addressing mode.");
@@ -220,7 +234,8 @@ function test_lda() {
   test("Ensure that LDA stack relative works for 8-bit memory/accumulator "+
        "mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9fe48a90148a900a302");
+    cpu.load_binary("18fba9fe48a90148a900a302", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfe, "The accumulator should be 0xfe when LDA loads "+
                           "an 8-bit value from the stack using LDA stack "+
                           "relative addressing mode.");
@@ -232,7 +247,8 @@ function test_lda() {
   test("Ensure that LDA stack relative works for 16-bit memory/accumulator "+
        "mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9fefa48a9010048a90000a303");
+    cpu.load_binary("18fbc220a9fefa48a9010048a90000a303", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfafe, "The accumulator should be 0xfafe when LDA "+
                             "loads a 16-bit value from the stack using LDA "+
                             "stack relative addressing mode.");
@@ -244,7 +260,8 @@ function test_lda() {
   test("Ensure that LDA absolute long works for 8-bit memory/accumulator "+
        "mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9fa8fffeeaaa900afffeeaa");
+    cpu.load_binary("18fba9fa8fffeeaaa900afffeeaa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfa, "The accumulator should be 0xfa when LDA "+
                           "loads an 8-bit value from $aaeeff using "+
                           "absolute long addressing mode.");
@@ -256,7 +273,8 @@ function test_lda() {
   test("Ensure that LDA absolute long works for 16-bit memory/accumulator "+
        "mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9fefa8fffeeaaa90000afffeeaa");
+    cpu.load_binary("18fbc220a9fefa8fffeeaaa90000afffeeaa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfafe, "The accumulator should be 0xfafe when LDA "+
                             "loads a 16-bit value from $aaeeff using "+
                             "absolute long addressing mode.");
@@ -268,7 +286,8 @@ function test_lda() {
   test("Ensure that LDA absolute long indexed by the x register works for "+
        "8-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9fe8fffeeaaa202a900bffdeeaa");
+    cpu.load_binary("18fba9fe8fffeeaaa202a900bffdeeaa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfe, "The accumulator should be 0xfe when LDA "+
                           "loads an 8-bit value from $aaeeff using "+
                           "absolute long indexed x addressing mode.");
@@ -282,7 +301,8 @@ function test_lda() {
   test("Ensure that LDA absolute long indexed by the x register works for "+
        "16-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9fefa8fffeeaaa203a90000bffceeaa");
+    cpu.load_binary("18fbc220a9fefa8fffeeaaa203a90000bffceeaa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfafe, "The accumulator should be 0xfafe when LDA "+
                             "loads a 16-bit value from $aaeeff using "+
                             "absolute long indexed x addressing mode."); 
@@ -299,7 +319,8 @@ function test_stz() {
   module("STZ");
   test("Test STZ direct page for 8-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9ff85fa64faa5fa");
+    cpu.load_binary("18fba9ff85fa64faa5fa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "The accumulator should be zero after loading from a "+
                        "direct page addresss that has had zero stored to it.");
     equals(cpu.p.e, 0, "The hidden e flag should be zero for native mode.");
@@ -308,7 +329,8 @@ function test_stz() {
   });
   test("Test STZ direct page for 16-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9ffff85fa64faa5fa");
+    cpu.load_binary("18fbc220a9ffff85fa64faa5fa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "The accumulator should be zero after loading from a "+
                        "direct page address that had zero stored to it.");
     equals(cpu.p.e, 0, "The hidden e flag should be zero for native mode.");
@@ -317,7 +339,8 @@ function test_stz() {
   });
   test("Test STZ absolute for 8-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9ff8d34129c3412ad3412");
+    cpu.load_binary("18fba9ff8d34129c3412ad3412", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "The accumulator should be zero after loading from an "+
                        "absolute address that had zero stored to it.");
     equals(cpu.p.e, 0, "The hidden e flag should be zero for native mode.");
@@ -326,7 +349,8 @@ function test_stz() {
   });
   test("Test STZ absolute for 16-bit memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9ffff8d34129c3412ad3412");
+    cpu.load_binary("18fbc220a9ffff8d34129c3412ad3412", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "The accumulator should be zero after loading from an "+
                        "absolute page address that had zero stored to it.");
     equals(cpu.p.e, 0, "The hidden e flag should be zero for native mode.");
@@ -336,7 +360,8 @@ function test_stz() {
   test("Test STZ direct page indexed by the x register for 8-bit "+
        "memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9ff85fb85faa20174faa5fb");
+    cpu.load_binary("18fba9ff85fb85faa20174faa5fb", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "The accumulator should be zero after loading from a "+
                        "direct page addresss that has had zero stored to it.");
     equals(cpu.p.e, 0, "The hidden e flag should be zero for native mode.");
@@ -346,7 +371,8 @@ function test_stz() {
   test("Test STZ direct page indexed by the x register for 16-bit "+
        "memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9ffff85faa20274f8a5fa");
+    cpu.load_binary("18fbc220a9ffff85faa20274f8a5fa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "The accumulator should be zero after loading from a "+
                        "direct page address that had zero stored to it.");
     equals(cpu.p.e, 0, "The hidden e flag should be zero for native mode.");
@@ -356,7 +382,8 @@ function test_stz() {
   test("Test STZ absolute indexed by the x register for 8-bit "+
        "memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fba9ff8dbbaa8dbaaaa2019ebaaaadbbaa");
+    cpu.load_binary("18fba9ff8dbbaa8dbaaaa2019ebaaaadbbaa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "The accumulator should be zero after loading from an "+
                        "absolute address that had zero stored to it.");
     equals(cpu.p.e, 0, "The hidden e flag should be zero for native mode.");
@@ -366,7 +393,8 @@ function test_stz() {
   test("Test STZ absolute indexed by the x register for 16-bit "+
        "memory/accumulator mode.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220a9ffff8dbbaaa2029eb9aaadbbaa");
+    cpu.load_binary("18fbc220a9ffff8dbbaaa2029eb9aaadbbaa", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "The accumulator should be zero after loading from an "+
                        "absolute page address that had zero stored to it.");
     equals(cpu.p.e, 0, "The hidden e flag should be zero for native mode.");
@@ -380,7 +408,8 @@ function test_emulation_mode() {
   test("Make sure pulling from the stack when the stack register is at 0x1ff"+
        "causes the stack register to pull from 0x100.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("a9fe8d0001a90068");
+    cpu.load_binary("a9fe8d0001a90068", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.s, 0, "The stack register should be 0 after the pull "+
                        "operation.");
     equals(cpu.r.a, 0xfe,  "The accumulator should be 0xfe after the pull "+
@@ -392,7 +421,9 @@ function test_mvn_and_mvp() {
   module("MVN and MVP");
   test("Test a short example program for MVP", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbe230a9ab8dff0fa9cd8d0010c230a90100a20010a00020440000");
+    cpu.load_binary("18fbe230a9ab8dff0fa9cd8d0010c230a90100a20010a00020440000",
+                    0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xffff, "After executing the example program the "+
                             "accumulator should've underflowed and "+
                             "resulted in 0xffff.");
@@ -415,7 +446,8 @@ function test_subroutines() {
     var cpu = new CPU_65816();
     // It jumps to 0xffff so it doesn't execute the subroutine again and 
     // effectively halts the program.
-    cpu.execute("18fbc23018a9ffff200e804cffff3a60");
+    cpu.load_binary("18fbc23018a9ffff200e804cffff3a60", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xfffe, "The subroutine should execute exactly once, "+
                             "decrementing 0xffff to 0xfffe."); 
   });
@@ -425,7 +457,8 @@ function test_cmp() {
   module("CMP");
   test("Compare two 8-bit numbers, 0x01 and 0xff", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbe23018a901c9ff");
+    cpu.load_binary("18fbe23018a901c9ff", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x01, "CMP should not change the value of the "+
                           "accumulator");
     equals(cpu.p.z, 0, "When comparing 0x01 and 0xff the zero(z) bit "+
@@ -437,7 +470,8 @@ function test_cmp() {
   });
   test("Compare two 16-bit numbers, 0xff01 and 0xfeff", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc23018a901ffc9fffe");
+    cpu.load_binary("18fbc23018a901ffc9fffe", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xff01, "CMP should not change the value of the "+
                             "accumulator");
     equals(cpu.p.n, 0, "When comparing 0xff01 and 0xfeff the negative(n) "+
@@ -454,7 +488,8 @@ function test_sbc() {
   test("Test normal subtraction of two 8-bit numbers that don't cause a "+
        "borrow.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbe230a90138e901");
+    cpu.load_binary("18fbe230a90138e901", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "0x01 - 0x01 should result in zero when using "+
                        "SBC");
     equals(cpu.p.z, 1, "0x01 - 0x01 should set the zero(z) bit when "+
@@ -470,7 +505,8 @@ function test_sbc() {
   test("Test normal subtraction of two 16-bit numbers that don't cause a "+
        "borrow.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc230a9010038e90100");
+    cpu.load_binary("18fbc230a9010038e90100", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0, "0x0001 - 0x0001 should result in zero when using "+
                        "SBC");
     equals(cpu.p.z, 1, "0x0001 - 0x0001 should set the zero(z) bit when "+
@@ -485,7 +521,8 @@ function test_sbc() {
   test("Test subtraction that triggers a borrow with 8-bit numbers", 
        function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbe230a9d038e9ef");
+    cpu.load_binary("18fbe230a9d038e9ef", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xe1, "0xd0 - 0xef should set the accumulator to 0xe1 "+
                           "when using SBC");
     equals(cpu.p.n, 1,    "0xd0 - 0xef should set the negative(n) bit when "+ 
@@ -500,7 +537,8 @@ function test_sbc() {
   test("Test subtraction that triggers a borrow with 16-bit numbers", 
        function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc230a900d038e900ef");
+    cpu.load_binary("18fbc230a900d038e900ef", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0xe100, "0xd000 - 0xef00 should set the accumulator to "+
                             "0xe0ff when using SBC");
     equals(cpu.p.n, 1, "0xd000 - 0xef00 should set the negative(n) bit when "+ 
@@ -515,7 +553,8 @@ function test_sbc() {
   test("Test subtraction with decimal mode on with two single digit 8-bit "+
        "numbers.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbf8a90938e905");
+    cpu.load_binary("18fbf8a90938e905", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 4, "The accumulator should be 4 after subtracting 0x5 "+
                        "0x9 with decimal mode on with 8-bit "+
                        "memory/accumulator mode.");
@@ -529,7 +568,8 @@ function test_sbc() {
   test("Test subtraction with decimal mode on with two double digit 8-bit "+
        "numbers.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbf8a99038e949");
+    cpu.load_binary("18fbf8a99038e949", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x41, "The accumulator should be 41 after subtracting 0x49 "+
                           "from 0x90 with decimal mode on with 8-bit "+
                           "memory/accumulator mode.");
@@ -543,7 +583,8 @@ function test_sbc() {
   test("Test subtraction with decimal mode on with 8-bit numbers that causes "+
        "a borrow.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbf8a91038e920");
+    cpu.load_binary("18fbf8a91038e920", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x90, "The accumulator should be 0x90 after subtracting "+
                           "0x20 from 0x10 with decimal and 8-bit "+
                           "memory/accumulator modes.");
@@ -557,7 +598,8 @@ function test_sbc() {
   test("Test subtraction of two single digit 16-bit numbers with decimal "+
        "mode set.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220f8a9050038e90200");
+    cpu.load_binary("18fbc220f8a9050038e90200", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x03, "The accumulator should be 0x03 after subtracting "+
                           "0x02 from 0x05 with decimal and 16-bit "+
                           "memory/accumulator modes.");
@@ -571,7 +613,8 @@ function test_sbc() {
   test("Test subtraction of two four digit 16-bit numbers with decimal "+
        "mode set.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220f8a9999938e91111");
+    cpu.load_binary("18fbc220f8a9999938e91111", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x8888, "The accumulator should be 0x8888 after "+
                             "subtracting 0x1111 from 0x9999 with decimal "+
                             "and 16-bit memory/accumulator modes.");
@@ -585,7 +628,8 @@ function test_sbc() {
   test("Test subtraction of two four digit 16-bit numbers with decimal "+
        "mode set that causes a borrow.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc220f8a9111138e99999");
+    cpu.load_binary("18fbc220f8a9111138e99999", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x1112, "The accumulator should be 0x1112 after "+
                             "subtracting 0x9999 from 0x1111 with decimal "+
                             "and 16-bit memory/accumulator modes.");
@@ -603,7 +647,8 @@ function test_adc() {
   test("Test normal addition of two 16-bit numbers that don't cause an "+
        "overflow (m bit is 0)", function() {
      var cpu = new CPU_65816();
-     cpu.execute("18fb18c230a90100690100");
+     cpu.load_binary("18fb18c230a90100690100", 0x8000);
+     cpu.execute(0x8000);
      equals(cpu.r.a, 2, "0x0001 + 0x0001 should result in 0x0002 when using "+
                         "ADC");
      equals(cpu.p.n, 0, "0x0001 + 0x0001 does not result in a negative "+
@@ -618,7 +663,8 @@ function test_adc() {
    test("Test normal addition of two 8-bit numbers that don't cause an "+
        "overflow (m bit is 1)", function() {
      var cpu = new CPU_65816();
-     cpu.execute("18fb18e230a9016901");
+     cpu.load_binary("18fb18e230a9016901", 0x8000);
+     cpu.execute(0x8000);
      equals(cpu.r.a, 2, "0x01 + 0x01 should result in 0x02 when using "+
                         "ADC");
      equals(cpu.p.n, 0, "0x01 + 0x01 does not result in a negative "+
@@ -634,7 +680,8 @@ function test_adc() {
   test("Test that overflow sets the carry flag and works in general with two"+
        "16-bit numbers (m bit is 0)", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18c230a9ffff690100");
+    cpu.load_binary("18fb18c230a9ffff690100", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.p.c, 1, "0xffff + 0x0001 should set the carry bit when using "+
                        "ADC");
     equals(cpu.r.a, 0, "0xffff + 0x0001 should result in the accumulator "+
@@ -650,7 +697,8 @@ function test_adc() {
   test("Test that overflow sets the carry flag and works in general with two"+
        "8-bit numbers (m bit is 1)", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18e230a9ff6901");
+    cpu.load_binary("18fb18e230a9ff6901", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.p.c, 1, "0xff + 0x01 should set the carry bit when using "+
                        "ADC");
     equals(cpu.r.a, 0, "0xff + 0x01 should result in the accumulator "+
@@ -665,7 +713,8 @@ function test_adc() {
 
   test("Test signed overflow with two 8-bit numbers (m bit is 1)", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18e230a97f6901");
+    cpu.load_binary("18fb18e230a97f6901", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x80, "0x7f + 0x01 should result in 0x80 when "+
                             "using ADC");
     equals(cpu.p.v, 1, "0x7f + 0x01 should set the overflow(v) bit when "+
@@ -679,7 +728,8 @@ function test_adc() {
   });
   test("Test signed overflow with two 16-bit numbers (m bit is 0)", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18c230a9ff7f690100");
+    cpu.load_binary("18fb18c230a9ff7f690100", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x8000, "0x7fff + 0x0001 should result in 0x8000 when "+
                             "using ADC");
     equals(cpu.p.v, 1, "0x7fff + 0x0001 should set the overflow(v) bit when "+
@@ -694,7 +744,8 @@ function test_adc() {
 
   test("Test ADC direct page with 8-bit numbers (m bit is 1)", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18e230a90185ffa97f65ff");
+    cpu.load_binary("18fb18e230a90185ffa97f65ff", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x80, "0x7f + 0x01 should result in 0x80 when "+
                             "using ADC");
     equals(cpu.p.v, 1, "0x7f + 0x01 should set the overflow(v) bit when "+
@@ -709,7 +760,8 @@ function test_adc() {
 
   test("Test ADC direct page with 16-bit numbers (m bit is 0)", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18c230a9010085fea9ff7f65fe");
+    cpu.load_binary("18fb18c230a9010085fea9ff7f65fe", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x8000, "0x7fff + 0x0001 should result in 0x8000 when "+
                             "using ADC");
     equals(cpu.p.v, 1, "0x7fff + 0x0001 should set the overflow(v) bit when "+
@@ -724,7 +776,8 @@ function test_adc() {
  
   test("Test ADC absolute with 8-bit numbers (m bit is 1)", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18e230a9018dffffa97f6dffff");
+    cpu.load_binary("18fb18e230a9018dffffa97f6dffff", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x80, "0x7f + 0x01 should result in 0x80 when "+
                             "using ADC");
     equals(cpu.p.v, 1, "0x7f + 0x01 should set the overflow(v) bit when "+
@@ -739,7 +792,8 @@ function test_adc() {
 
   test("Test ADC absolute with 16-bit numbers (m bit is 0)", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18c230a901008dffffa9ff7f6dffff");
+    cpu.load_binary("18fb18c230a901008dffffa9ff7f6dffff", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x8000, "0x7fff + 0x0001 should result in 0x8000 when "+
                             "using ADC");
     equals(cpu.p.v, 1, "0x7fff + 0x0001 should set the overflow(v) bit when "+
@@ -755,7 +809,8 @@ function test_adc() {
   test("Test ADC direct page indirect with 8-bit numbers (m bit is 1)", 
        function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18e230a90185ffa9ff85fd64fea97f72fd");
+    cpu.load_binary("18fb18e230a90185ffa9ff85fd64fea97f72fd", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x80, "0x7f + 0x01 should result in 0x80 when "+
                             "using ADC");
     equals(cpu.p.v, 1, "0x7f + 0x01 should set the overflow(v) bit when "+
@@ -770,7 +825,8 @@ function test_adc() {
   test("Test ADC direct page indirect with 16-bit numbers (m bit is 0)", 
        function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18c230a901008500a9000085bba9ff7f72bb");
+    cpu.load_binary("18fb18c230a901008500a9000085bba9ff7f72bb", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x8000, "0x7fff + 0x0001 should result in 0x8000 when "+
                             "using ADC");
     equals(cpu.p.v, 1, "0x7fff + 0x0001 should set the overflow(v) bit when "+
@@ -786,7 +842,8 @@ function test_adc() {
   test("Test that ADC handles decimal mode with legal BCD numbers in 8-bit "+
        "memory/accumulator mode with single digit numbers.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18f8a9056905");
+    cpu.load_binary("18fb18f8a9056905", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x10, "0x05 + 0x05 should result in 0x10 with decimal "+
                           "mode on and with 8-bit memory/accumulator mode.");
     equals(cpu.p.c, 0, "The carry flag of the p status register should be "+
@@ -801,7 +858,8 @@ function test_adc() {
   test("Test that ADC handles decimal mode with legal BCD numbers in 8-bit "+
        "memory/accumulator mode with double digit numbers.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18f8a9156926");
+    cpu.load_binary("18fb18f8a9156926", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x41, "0x15 + 0x26 should result in 0x41 with decimal "+
                           "mode on and with 8-bit memory/accumulator mode.");
     equals(cpu.p.c, 0, "The carry flag of the p status register should be "+
@@ -817,7 +875,8 @@ function test_adc() {
        "memory/accumulator mode with double digit numbers with the carry "+
        "bit set", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb38f8a9156926");
+    cpu.load_binary("18fb38f8a9156926", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x42, "0x15 + 0x26 should result in 0x42 with decimal "+
                           "mode on and with 8-bit memory/accumulator mode "+
                           "and the carry bit set.");
@@ -834,7 +893,8 @@ function test_adc() {
        "memory/accumulator mode when adding two numbers that cause an "+
        "overflow.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18f8a9556960");
+    cpu.load_binary("18fb18f8a9556960", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x16, "0x55 + 0x60 should result in 0x16 with decimal "+
                           "mode on and with 8-bit memory/accumulator mode.");
     equals(cpu.p.c, 1, "The carry flag of the p status register should be "+
@@ -850,7 +910,8 @@ function test_adc() {
        "memory/accumulator mode when adding two single digit numbers.", 
        function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18f8c220a90100690900");
+    cpu.load_binary("18fb18f8c220a90100690900", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x10, "0x0001 + 0x0009 should result in 0x0010 with "+
                           "decimal mode on and with 16-bit "+
                           "memory/accumulator mode.");
@@ -867,7 +928,8 @@ function test_adc() {
        "memory/accumulator mode when adding two four digit numbers.", 
        function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18f8c220a90110699939");
+    cpu.load_binary("18fb18f8c220a90110699939", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x5000, "0x1001 + 0x3999 should result in 0x5000 with "+
                             "decimal mode on and with 16-bit "+
                             "memory/accumulator mode.");
@@ -884,7 +946,8 @@ function test_adc() {
        "memory/accumulator mode when adding two numbers that cause an "+
        "overflow.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb18f8c220a99756699999");
+    cpu.load_binary("18fb18f8c220a99756699999", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x5697, "0x5697 + 0x9999 should result in 0x5697 with "+
                             "decimal mode on and with 16-bit "+
                             "memory/accumulator mode.");
@@ -901,7 +964,8 @@ function test_adc() {
        "memory/accumulator mode when adding two four digit numbers with the "+
        "carry bit set.", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fb38f8c220a90110699939");
+    cpu.load_binary("18fb38f8c220a90110699939", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x5001, "0x1001 + 0x3999 should result in 0x5001 with "+
                             "decimal mode on and with 16-bit "+
                             "memory/accumulator mode and the carry flag set.");
@@ -921,9 +985,8 @@ function test_branching() {
   test("Test that BRA with 0x00 as its argument doesn't increment or "+
        "decrement the program counter", function() {
     var cpu = new CPU_65816();
-    cpu.execute("8000");
-    // NOTE: 0x8003 is subject to change however I decide to lay out memory
-    // eventually.
+    cpu.load_binary("8000", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.pc, 0x8003, "Make sure that the program counter isn't "+
                              "incremented or decremented if BRA is given "+
                              "0x00 as its argument.");
@@ -932,12 +995,16 @@ function test_branching() {
   test("Check that the branching operations properly treat the argument as "+
        "a two's complement number", function() {
     var cpu = new CPU_65816();
-    cpu.execute("80f0"); // negative two's complement number 0xf0 = -16
+    // negative two's complement number 0xf0 = -16
+    cpu.load_binary("80f0", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.pc, (0x8003-16), "A branching operation when given a "+
                                   "negative two's complement number should "+
                                   "decrement the program counter by the "+
-                                  "proper amount.");    
-    cpu.execute("8020"); // positive two's complement number.
+                                  "proper amount.");
+    cpu.reset();
+    cpu.load_binary("8020", 0x8000); // positive two's complement number.
+    cpu.execute(0x8000);
     equals(cpu.r.pc, (0x8003+0x20), "A branching operation when given a "+
                                     "positive two's complement number should "+
                                     "increment the program counter by the "+
@@ -946,14 +1013,16 @@ function test_branching() {
   
   test("Check that BPL works as expected", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc230a9fe7f1a10fd");
+    cpu.load_binary("18fbc230a9fe7f1a10fd", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x8000, "Check that branching only occurs while the "+
                             "number is a two's complement positive number.");
   });
 
   test("Check that BMI works as expected", function() {
     var cpu = new CPU_65816();
-    cpu.execute("18fbc230a901803a30fd");
+    cpu.load_binary("18fbc230a901803a30fd", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.r.a, 0x7fff, "Check that branching only occurs while the "+
                             "number is a two's complement negative number.");
   });
@@ -964,7 +1033,8 @@ function test_sep() {
   test("Test 'SEP #$30' not in emulation mode", function() {
     var cpu = new CPU_65816();
     cpu.p.e = 0;
-    cpu.execute("e230");
+    cpu.load_binary("e230", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.p.m, 1, "'SEP #$30' should set the m status bit of the p "+
                        "register to 1");
     equals(cpu.p.x, 1, "'SEP #$30' should set the x status bit of the p "+
@@ -985,7 +1055,8 @@ function test_sep() {
   test("Test 'SEP #$cf' not in emulation mode", function() {
     var cpu = new CPU_65816();
     cpu.p.e = 0;
-    cpu.execute("e2cf"); 
+    cpu.load_binary("e2cf", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.p.m, 0, "'SEP #$cf' should not set the m status bit of the p "+
                        "register to 1");
     equals(cpu.p.x, 0, "'SEP #$cf' should not set the x status bit of the p "+
@@ -1019,7 +1090,8 @@ function test_rep() {
     cpu.p.x = 1;
     cpu.p.m = 1;
     cpu.p.z = 1;
-    cpu.execute("c230");
+    cpu.load_binary("c230", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.p.m, 0, "'REP #$30' should clear the m bit of the p status "+
                        "register");
     equals(cpu.p.x, 0, "'REP #$30' should clear the x bit of the p status "+
@@ -1050,7 +1122,8 @@ function test_rep() {
     cpu.p.x = 1;
     cpu.p.m = 1;
     cpu.p.z = 1;
-    cpu.execute("c2cf");
+    cpu.load_binary("c2cf", 0x8000);
+    cpu.execute(0x8000);
     equals(cpu.p.m, 1, "'REP #$cf' should not clear the m bit of the p "+
                        "status register");
     equals(cpu.p.x, 1, "'REP #$cf' should not clear the x bit of the p "+