diff --git a/include/instructions.h b/include/instructions.h
index 67b51e7..f1de068 100644
--- a/include/instructions.h
+++ b/include/instructions.h
@@ -29,6 +29,7 @@ public:
   void add_rm32_r32();  // 0x01
   void xor_rm32_r32();  // 0x31
   void dec_ecx();       // 0x49
+  void opcode_83();     // 0x83
   void mov_rm32_r32();  // 0x89
   void nop();           // 0x90
   void mov_ecx_imm32(); // 0xb9
@@ -37,5 +38,5 @@ public:
   void hlt();           // 0xf4
   void opcode_ff();     // 0xff
 
-  void cmp_rm32_imm8();
+  void cmp_rm32_imm8(); // called by opcode_83
 };
diff --git a/instructions.cpp b/instructions.cpp
index f9442ea..1409a06 100644
--- a/instructions.cpp
+++ b/instructions.cpp
@@ -23,6 +23,7 @@ void Instructions::init_instructions(){
   this->instructions[0x01] = &Instructions::add_rm32_r32;
   this->instructions[0x31] = &Instructions::xor_rm32_r32;
   this->instructions[0x49] = &Instructions::dec_ecx;
+  this->instructions[0x83] = &Instructions::opcode_83;
   this->instructions[0x89] = &Instructions::mov_rm32_r32;
   this->instructions[0x90] = &Instructions::nop;
   this->instructions[0xb9] = &Instructions::mov_ecx_imm32;
@@ -153,6 +154,21 @@ void Instructions::dec_ecx(){
   this->registers[1]--;
 }
 
+void Instructions::opcode_83(){
+  printf("opcode_83 called.\n");
+
+  this->modrm = memory.read_uint8(this->eip);
+  this->calc_modrm();
+
+  switch (this->R) {
+    case 7:
+      cmp_rm32_imm8();
+      break;
+    default:
+      break;
+  }
+}
+
 void Instructions::mov_rm32_r32(){
   printf("mov_rm32_r32 called.\n");
   uint32_t addr, imm32;
@@ -255,14 +271,14 @@ void Instructions::opcode_ff(){
 void Instructions::cmp_rm32_imm8(){
   printf("cmp_rm32_imm8 called.\n");
 
-  this->modrm = memory.read_uint8(this->eip);
-  this->calc_modrm();
-
   this->eip++;
   uint8_t imm8 = memory.read_uint8(this->eip);
+  printf("imm8: 0x%08x (%d)\n", imm8, imm8);
   uint32_t result = this->registers[this->M] - imm8;
 
   set_flag(!result, ZF);
+
+  this->eip++;
 }
 
 void Instructions::set_flag(int flag, uint32_t flag_type){