diff --git a/src/mame/drivers/atarist.cpp b/src/mame/drivers/atarist.cpp
index 0ed90004cfa..2314bf04cc4 100644
--- a/src/mame/drivers/atarist.cpp
+++ b/src/mame/drivers/atarist.cpp
@@ -1940,6 +1940,10 @@ void ste_state::machine_start()
 	m_mfp->i4_w(1);
 	m_mfp->i5_w(1);
 	m_mfp->i7_w(1);
+
+	m_shifter_base=0;
+	m_shifter_ofs=0;
+	m_shifter_mode=0;
 }
 
 
diff --git a/src/mame/drivers/hng64.cpp b/src/mame/drivers/hng64.cpp
index 40145c4456e..e8725b975bc 100644
--- a/src/mame/drivers/hng64.cpp
+++ b/src/mame/drivers/hng64.cpp
@@ -1775,6 +1775,8 @@ void hng64_state::machine_start()
 		m_videoregs[i] = 0xdeadbeef;
 	}
 
+	m_irq_pending = 0;
+
 	m_3dfifo_timer = machine().scheduler().timer_alloc(timer_expired_delegate(FUNC(hng64_state::hng64_3dfifo_processed), this));
 	m_comhack_timer = machine().scheduler().timer_alloc(timer_expired_delegate(FUNC(hng64_state::comhack_callback), this));
 
diff --git a/src/mame/drivers/system1.cpp b/src/mame/drivers/system1.cpp
index 15a8f97d07e..ad5cb24c811 100644
--- a/src/mame/drivers/system1.cpp
+++ b/src/mame/drivers/system1.cpp
@@ -388,6 +388,7 @@ void system1_state::machine_start()
 	m_maincpu->z80_set_cycle_tables(cc_op, cc_cb, cc_ed, cc_xy, cc_xycb, cc_ex);
 
 	m_mute_xor = 0x00;
+	m_dakkochn_mux_data = 0x00;
 
 	save_item(NAME(m_dakkochn_mux_data));
 	save_item(NAME(m_videomode_prev));
@@ -407,7 +408,6 @@ MACHINE_START_MEMBER(system1_state,system2)
 
 void system1_state::machine_reset()
 {
-	m_dakkochn_mux_data = 0;
 }
 
 
diff --git a/src/mame/drivers/taitowlf.cpp b/src/mame/drivers/taitowlf.cpp
index 5ce7ccf8f40..0ffa09aa2db 100644
--- a/src/mame/drivers/taitowlf.cpp
+++ b/src/mame/drivers/taitowlf.cpp
@@ -62,6 +62,9 @@ TODO:
 #include "emupal.h"
 #include "screen.h"
 
+
+namespace {
+
 class taitowlf_state : public pcat_base_state
 {
 public:
@@ -328,6 +331,8 @@ void taitowlf_state::taitowlf_io(address_map &map)
 
 void taitowlf_state::machine_start()
 {
+	for (int i = 0; i < 4; i++)
+		std::fill(std::begin(m_piix4_config_reg[i]), std::end(m_piix4_config_reg[i]), 0);
 }
 
 void taitowlf_state::machine_reset()
@@ -428,6 +433,9 @@ ROM_START(pf2012)
 	ROM_LOAD("e58-04.u71", 0x000000, 0x20000, CRC(500e6113) SHA1(93226706517c02e336f96bdf9443785158e7becf) )
 ROM_END
 
+} // Anonymous namespace
+
+
 /*****************************************************************************/
 
 GAME(1997, pf2012, 0,   taitowlf, 0, taitowlf_state, init_taitowlf, ROT0, "Taito",  "Psychic Force 2012", MACHINE_NOT_WORKING | MACHINE_NO_SOUND)
diff --git a/src/mame/drivers/viper.cpp b/src/mame/drivers/viper.cpp
index 5b114d6f603..0c244f28d21 100644
--- a/src/mame/drivers/viper.cpp
+++ b/src/mame/drivers/viper.cpp
@@ -360,6 +360,8 @@ some other components. It will be documented at a later date.
 #include "speaker.h"
 
 
+namespace {
+
 #define VIPER_DEBUG_LOG
 #define VIPER_DEBUG_EPIC_INTS       0
 #define VIPER_DEBUG_EPIC_TIMERS     0
@@ -393,6 +395,10 @@ public:
 
 	DECLARE_READ_LINE_MEMBER(ds2430_unk_r);
 
+protected:
+	virtual void machine_start() override;
+	virtual void machine_reset() override;
+
 private:
 	uint32_t epic_r(offs_t offset);
 	void epic_w(offs_t offset, uint32_t data);
@@ -435,9 +441,6 @@ private:
 
 	void viper_map(address_map &map);
 
-	virtual void machine_start() override;
-	virtual void machine_reset() override;
-
 	TIMER_CALLBACK_MEMBER(epic_global_timer_callback);
 	TIMER_CALLBACK_MEMBER(ds2430_timer_callback);
 
@@ -2374,20 +2377,20 @@ void viper_state::machine_start()
 	save_item(NAME(m_epic.i2c_cr));
 	save_item(NAME(m_epic.i2c_sr));
 	save_item(NAME(m_epic.i2c_state));
-	for (int i = 0; i < MPC8240_NUM_INTERRUPTS; i ++)
-	{
-		save_item(NAME(m_epic.irq[i].vector), i);
-		save_item(NAME(m_epic.irq[i].priority), i);
-		save_item(NAME(m_epic.irq[i].destination), i); // written but never read
-		save_item(NAME(m_epic.irq[i].active), i);
-		save_item(NAME(m_epic.irq[i].pending), i);
-		save_item(NAME(m_epic.irq[i].mask), i);
-	}
-	for (int i = 0; i < 4; i ++)
-	{
-		save_item(NAME(m_epic.global_timer[i].base_count), i);
-		save_item(NAME(m_epic.global_timer[i].enable), i);
-	}
+
+	save_item(STRUCT_MEMBER(m_epic.irq, vector));
+	save_item(STRUCT_MEMBER(m_epic.irq, priority));
+	save_item(STRUCT_MEMBER(m_epic.irq, destination)); // written but never read
+	save_item(STRUCT_MEMBER(m_epic.irq, active));
+	save_item(STRUCT_MEMBER(m_epic.irq, pending));
+	save_item(STRUCT_MEMBER(m_epic.irq, mask));
+
+	save_item(STRUCT_MEMBER(m_epic.global_timer, base_count));
+	save_item(STRUCT_MEMBER(m_epic.global_timer, enable));
+
+	m_ds2430_data_count = 0;
+	m_ds2430_state = 0;
+	m_ds2430_reset = 0;
 }
 
 void viper_state::machine_reset()
@@ -3053,6 +3056,10 @@ ROM_START(mfightcc) //*
 	DISK_IMAGE( "c09c04", 0, SHA1(bf5f7447d74399d34edd4eb6dfcca7f6fc2154f2) )
 ROM_END
 
+
+} // Anonymous namespace
+
+
 /*****************************************************************************/
 
 /* Viper BIOS */