diff --git a/src/devices/cpu/gigatron/gigatron.cpp b/src/devices/cpu/gigatron/gigatron.cpp
index 6c25f4abd52..78e3a19afb2 100644
--- a/src/devices/cpu/gigatron/gigatron.cpp
+++ b/src/devices/cpu/gigatron/gigatron.cpp
@@ -13,7 +13,7 @@
 #include "gigatrondasm.h"
 
 
-DEFINE_DEVICE_TYPE(GTRON, gigatron_cpu_device, "gigatron_cpu", "Gigatron CPU")
+DEFINE_DEVICE_TYPE(GTRON, gigatron_cpu_device, "gigatron_cpu", "Gigatron")
 
 
 /* FLAGS */
@@ -24,7 +24,6 @@ DEFINE_DEVICE_TYPE(GTRON, gigatron_cpu_device, "gigatron_cpu", "Gigatron CPU")
 #define C  0x10
 #endif
 
-
 #define gigatron_readop(A) m_program->read_word(A)
 #define gigatron_readmem16(A) m_data->read_dword(A)
 #define gigatron_readmem8(A) m_data->read_byte(A)
@@ -52,7 +51,8 @@ void gigatron_cpu_device::execute_run()
 		debugger_instruction_hook(m_pc);
 
 		opcode = gigatron_readop(m_pc);
-		m_pc = m_npc++;
+		m_pc = m_npc;
+		m_npc = (m_pc + 1) & m_romMask;
 
 		uint8_t op = (opcode >> 13) & 0x0007;
 		uint8_t mode = (opcode >> 10) & 0x0007;
@@ -98,7 +98,7 @@ void gigatron_cpu_device::init()
 	m_x = 0;
 	m_y = 0;
 	m_pc = 0;
-	m_npc = (m_pc + 1);
+	m_npc = (m_pc + 1) & m_romMask;
 	m_ppc = 0;
 	m_inReg = 0xFF;
 
@@ -109,6 +109,7 @@ void gigatron_cpu_device::init()
 	state_add(GTRON_AC,        "AC",        m_ac);
 	state_add(GTRON_X,         "X",         m_x);
 	state_add(GTRON_Y,         "Y",         m_y);
+	state_add(GTRON_IREG,      "IREG",      m_inReg);
 
 	set_icountptr(m_icount);
 
@@ -121,6 +122,7 @@ void gigatron_cpu_device::init()
 	save_item(NAME(m_pc));
 
 	m_outx_cb.resolve_safe();
+	m_ir_cb.resolve_safe(0);
 }
 
 void gigatron_cpu_device::branchOp(uint8_t op, uint8_t mode, uint8_t bus, uint8_t d)
@@ -131,29 +133,29 @@ void gigatron_cpu_device::branchOp(uint8_t op, uint8_t mode, uint8_t bus, uint8_
 	uint16_t base = m_pc & 0xff00;
 	switch (mode)
 	{
-	case 0:
+	case 0: //jmp
 		c = true;
 		base = m_y << 8;
 		break;
-	case 1:
+	case 1: //bgt
 		c = (ac2 > ZERO);
 		break;
-	case 2:
+	case 2: //blt
 		c = (ac2 < ZERO);
 		break;
-	case 3:
+	case 3: //bne
 		c = (ac2 != ZERO);
 		break;
-	case 4:
+	case 4: //beq
 		c = (ac2 == ZERO);
 		break;
-	case 5:
+	case 5: //bge
 		c = (ac2 >= ZERO);
 		break;
-	case 6:
+	case 6: //ble
 		c = (ac2 <= ZERO);
 		break;
-	case 7:
+	case 7: //bra
 		c = true;
 		break;
 	}
@@ -219,7 +221,10 @@ void gigatron_cpu_device::aluOp(uint8_t op, uint8_t mode, uint8_t bus, uint8_t d
 	case 7:
 		uint16_t rising = ~(m_out & b);
 		if (rising & 0x40)
+		{
 			m_outx = m_ac;
+			m_outx_cb(0, m_outx, 0xFF);
+		}
 		break;
 	}
 }
@@ -313,10 +318,12 @@ void gigatron_cpu_device::execute_set_input(int irqline, int state)
 
 gigatron_cpu_device::gigatron_cpu_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
 	: cpu_device(mconfig, GTRON, tag, owner, clock)
-	, m_ramMask(0x7fff)
+	, m_ramMask(0x7FFF)
+	, m_romMask(0xFFFF)
 	, m_program_config("program", ENDIANNESS_BIG, 16, 14, -1)
 	, m_data_config("data", ENDIANNESS_BIG, 8, 15, 0)
 	, m_outx_cb(*this)
+	, m_ir_cb(*this)
 {
 }
 
diff --git a/src/devices/cpu/gigatron/gigatron.h b/src/devices/cpu/gigatron/gigatron.h
index 6cc1173d23c..50f359af21f 100644
--- a/src/devices/cpu/gigatron/gigatron.h
+++ b/src/devices/cpu/gigatron/gigatron.h
@@ -16,7 +16,7 @@
 enum
 {
 	GTRON_PC, GTRON_NPC,
-	GTRON_AC, GTRON_X, GTRON_Y
+	GTRON_AC, GTRON_X, GTRON_Y, GTRON_IREG
 };
 
 
@@ -26,6 +26,7 @@ public:
 	// construction/destruction
 	gigatron_cpu_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 	auto outx_cb() { return m_outx_cb.bind(); }
+	auto ir_cb() { return m_ir_cb.bind(); }
 
 protected:
 	// device-level overrides
@@ -61,6 +62,7 @@ protected:
 	uint16_t m_ppc;
 	uint8_t m_inReg;
 	uint16_t m_ramMask;
+	uint16_t m_romMask;
 	uint16_t m_out;
 	uint16_t m_outx;
 
@@ -79,6 +81,7 @@ private:
 	void gigatron_illegal();
 
 	devcb_write8 m_outx_cb;
+	devcb_read8 m_ir_cb;
 };
 
 
diff --git a/src/mame/drivers/gigatron.cpp b/src/mame/drivers/gigatron.cpp
index e589c88f201..30590ebc4a2 100644
--- a/src/mame/drivers/gigatron.cpp
+++ b/src/mame/drivers/gigatron.cpp
@@ -48,6 +48,7 @@ private:
 	}
 
 	void blinkenlights(uint8_t data);
+	uint8_t inputs();
 
 	required_device<gigatron_cpu_device> m_maincpu;
 	required_ioport m_io_inputs;
@@ -82,6 +83,11 @@ void gigatron_state::blinkenlights(uint8_t data)
 	lights_changed ^= light;
 }
 
+uint8_t gigatron_state::inputs()
+{
+	return m_io_inputs->read() ^ 0xFF;
+}
+
 static INPUT_PORTS_START(gigatron)
 	PORT_START("GAMEPAD")
 	PORT_BIT( 0x0004, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_PLAYER(1)
@@ -100,6 +106,7 @@ void gigatron_state::gigatron(machine_config &config)
 	m_maincpu->set_addrmap(AS_PROGRAM, &gigatron_state::prog_map);
 	m_maincpu->set_addrmap(AS_DATA, &gigatron_state::data_map);
 	m_maincpu->outx_cb().set(FUNC(gigatron_state::blinkenlights));
+	m_maincpu->ir_cb().set(FUNC(gigatron_state::inputs));
 
 	/* video hardware */
 	screen_device &screen(SCREEN(config, "screen", SCREEN_TYPE_RASTER));