diff --git a/src/mame/drivers/hh_sm510.cpp b/src/mame/drivers/hh_sm510.cpp
index 9a0d6d3e26d..02cfb643d04 100644
--- a/src/mame/drivers/hh_sm510.cpp
+++ b/src/mame/drivers/hh_sm510.cpp
@@ -8,9 +8,9 @@
   TODO:
   - add svg layout for gnw_mc25
   - improve svg layout for gnw_jr55, gnw_mw56
-  - confirm gnw_mc25 romdump
   - svg lcd screen background/foreground (not supported in core),
     or should it be for external artwork only?
+  - confirm gnw_mc25 rom (dumped from Soviet clone, but pretty confident that it's same)
 
 ***************************************************************************/
 
@@ -68,7 +68,7 @@ public:
 	u8 m_display_x_len;             // lcd number of groups
 	u8 m_display_y_len;             // lcd number of segments
 	u8 m_display_z_len;             // lcd number of commons
-	u32 m_display_state[0x20];      // lcd segment data
+	u32 m_display_state[0x20];      // lcd segment data (max. 5-bit offset)
 	u8 m_display_decay[0x20][0x20]; // (internal use)
 	u8 m_display_cache[0x20][0x20]; // (internal use)
 
@@ -608,7 +608,7 @@ MACHINE_CONFIG_END
   MC-25 and EG-26 are the same game, it's assumed that the latter was for
   regions where Nintendo wasn't able to license from Disney.
 
-  In 1984, Elektronika(USSR) released a clone, Nu, Pogodi! This was followed
+  In 1984, Elektronika(USSR) released a clone: Nu, Pogodi! This was followed
   by several other games that were the same under the hood, only differing
   in graphics.
 
@@ -628,22 +628,19 @@ public:
 
 static INPUT_PORTS_START( mc25 )
 	PORT_START("IN.0")
-	PORT_BIT( 0x01, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_1) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
-	PORT_BIT( 0x02, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_2) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
-	PORT_BIT( 0x04, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_3) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
-	PORT_BIT( 0x08, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_4) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
+	PORT_BIT( 0x0f, IP_ACTIVE_HIGH, IPT_UNUSED )
 
 	PORT_START("IN.1")
-	PORT_BIT( 0x01, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_Q) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
-	PORT_BIT( 0x02, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_W) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
-	PORT_BIT( 0x04, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_E) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
-	PORT_BIT( 0x08, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_R) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
+	PORT_BIT( 0x01, IP_ACTIVE_HIGH, IPT_JOYSTICKRIGHT_DOWN ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_16WAY
+	PORT_BIT( 0x02, IP_ACTIVE_HIGH, IPT_JOYSTICKRIGHT_UP ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_16WAY
+	PORT_BIT( 0x04, IP_ACTIVE_HIGH, IPT_JOYSTICKLEFT_DOWN ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_16WAY
+	PORT_BIT( 0x08, IP_ACTIVE_HIGH, IPT_JOYSTICKLEFT_UP ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_16WAY
 
 	PORT_START("IN.2")
-	PORT_BIT( 0x01, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_A) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
-	PORT_BIT( 0x02, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_S) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) // game b
-	PORT_BIT( 0x04, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_D) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) // game a
-	PORT_BIT( 0x08, IP_ACTIVE_HIGH, IPT_KEYPAD ) PORT_CODE(KEYCODE_F) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
+	PORT_BIT( 0x01, IP_ACTIVE_HIGH, IPT_SELECT ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_NAME("Time")
+	PORT_BIT( 0x02, IP_ACTIVE_HIGH, IPT_START2 ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_NAME("Game B")
+	PORT_BIT( 0x04, IP_ACTIVE_HIGH, IPT_START1 ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_NAME("Game A")
+	PORT_BIT( 0x08, IP_ACTIVE_HIGH, IPT_SERVICE2 ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_NAME("Alarm")
 
 	PORT_START("ACL")
 	PORT_BIT( 0x01, IP_ACTIVE_HIGH, IPT_SERVICE1 ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, acl_button, nullptr) PORT_NAME("ACL")