8 files changed, 43 insertions, 20 deletions
diff --git a/src/sim/controller.cc b/src/sim/controller.cc
index 833d900..17937eb 100644
--- a/src/sim/controller.cc
+++ b/src/sim/controller.cc
@@ -29,11 +29,11 @@ std::array<int, GPR_NUM> Controller::get_gprs() { return this->gprs; }
 
 int Controller::get_pc() { return this->pc; }
 
-Response Controller::advance(InstrDTO &i, Response p)
+Response Controller::advance(InstrDTO &next_instr, Response p)
 {
 	Response r;
 
-	r = this->next->advance(i, p);
+	r = this->next->advance(next_instr, p);
 	++this->clock_cycle;
 	return r;
 }
diff --git a/src/sim/ex.cc b/src/sim/ex.cc
index c9c2116..5b561f8 100644
--- a/src/sim/ex.cc
+++ b/src/sim/ex.cc
@@ -6,4 +6,4 @@
 
 EX::EX(Stage *stage) : Stage(stage) { this->id = EXEC; }
 
-Response EX::advance(InstrDTO &i, Response p) { return OK; }
+Response EX::advance(InstrDTO &next_instr, Response p) { return OK; }
diff --git a/src/sim/id.cc b/src/sim/id.cc
index 70fab9a..83a8751 100644
--- a/src/sim/id.cc
+++ b/src/sim/id.cc
@@ -8,15 +8,16 @@
 
 ID::ID(Stage *stage) : Stage(stage) { this->id = DCDE; }
 
-Response ID::advance(InstrDTO &i, Response p)
+Response ID::advance(InstrDTO &next_instr, Response p)
 {
 	Response r;
-	signed int s1, s2, s3;
-	Mnemonic m;
+	r = OK;
+	// signed int s1, s2, s3;
+	// Mnemonic m;
 
-	s1 = i.get_instr_bits();
+	// s1 = next_instr.get_instr_bits();
 
-	get_instr_fields(s1, s2, s3, m);
+	// get_instr_fields(s1, s2, s3, m);
 	return r;
 }
 
diff --git a/src/sim/if.cc b/src/sim/if.cc
index 099ff1c..de044f8 100644
--- a/src/sim/if.cc
+++ b/src/sim/if.cc
@@ -6,17 +6,31 @@
 
 IF::IF(Stage *stage) : Stage(stage) { this->id = FETCH; }
 
-Response IF::advance(InstrDTO &i, Response p)
+Response IF::advance(InstrDTO &next_instr, Response p)
+{
+	this->fetch_with_buffer();
+	if (this->status == OK && p == OK) {
+		// mutual consent
+		++this->pc;
+		this->curr_instr->set_time_of(this->id, this->clock_cycle);
+		next_instr = *this->curr_instr;
+		curr_instr = nullptr;
+	}
+	return this->status;
+}
+
+void IF::fetch_with_buffer()
 {
 	Response r;
 	signed int bits;
 
-	r = this->storage->read_word(this->id, this->pc, bits);
-	if (r == OK) {
-		++this->pc;
-		i.set_time_of(this->id, this->clock_cycle);
-		i.set_instr_bits(bits);
+	if (this->curr_instr == nullptr) {
+		r = this->storage->read_word(this->id, this->pc, bits);
+		if (r == OK) {
+			this->status = r;
+			this->curr_instr = std::make_unique<InstrDTO>();
+			this->curr_instr->set_instr_bits(bits);
+		} else
+			this->status = STALLED;
 	}
-
-	return r;
 }
diff --git a/src/sim/instrDTO.cc b/src/sim/instrDTO.cc
index 7418033..5a7fe3b 100644
--- a/src/sim/instrDTO.cc
+++ b/src/sim/instrDTO.cc
@@ -7,6 +7,7 @@ InstrDTO::InstrDTO()
 	this->s1 = 0;
 	this->s2 = 0;
 	this->s3 = 0;
+	this->mnemonic = NOP;
 }
 
 int InstrDTO::get_time_of(Accessor a) { return this->hist[a]; }
diff --git a/src/sim/mm.cc b/src/sim/mm.cc
index 93c5b87..f394420 100644
--- a/src/sim/mm.cc
+++ b/src/sim/mm.cc
@@ -6,7 +6,7 @@
 
 MM::MM(Stage *stage) : Stage(stage) { this->id = MEM; } 
 
-Response MM::advance(InstrDTO &i, Response p)
+Response MM::advance(InstrDTO &next_instr, Response p)
 {
 	return OK;
 }
diff --git a/src/sim/stage.cc b/src/sim/stage.cc
index 8d9dfc0..48ee494 100644
--- a/src/sim/stage.cc
+++ b/src/sim/stage.cc
@@ -5,7 +5,14 @@
 
 static Logger *global_log = Logger::getInstance();
 
-Stage::Stage(Stage *next) { this->next = next; }
+Stage::Stage(Stage *next)
+{
+	this->next = next;
+	this->curr_instr = nullptr;
+	this->status = OK;
+}
+
+Stage::~Stage() { delete this->next; };
 
 std::array<int, GPR_NUM> Stage::gprs;
 std::array<int, V_NUM> Stage::vrs;
@@ -19,7 +26,7 @@ Response Stage::check_out(unsigned int &v)
 {
 	Response r;
 	if (this->is_checked_out(v))
-		r = STALLED;
+		r = BLOCKED;
 	else {
 		r = OK;
 		v = this->check_out_register(v);
diff --git a/src/sim/wb.cc b/src/sim/wb.cc
index 13ab66a..bdea65a 100644
--- a/src/sim/wb.cc
+++ b/src/sim/wb.cc
@@ -6,4 +6,4 @@
 
 WB::WB(Stage *stage) : Stage(stage) { this->id = WRITE; }
 
-Response WB::advance(InstrDTO &i, Response p) { return OK; }
+Response WB::advance(InstrDTO &next_instr, Response p) { return OK; }