diff --git a/src/devices/cpu/unsp/unsp.cpp b/src/devices/cpu/unsp/unsp.cpp
index 9ac01d757df..7d1359896af 100644
--- a/src/devices/cpu/unsp/unsp.cpp
+++ b/src/devices/cpu/unsp/unsp.cpp
@@ -256,13 +256,13 @@ void unsp_device::state_import(const device_state_entry &entry)
 void unsp_device::update_nzsc(uint32_t value, uint16_t r0, uint16_t r1)
 {
 	m_core->m_r[REG_SR] &= ~(UNSP_N | UNSP_Z | UNSP_S | UNSP_C);
-	if((int16_t)r0 < (int16_t)r1)
+	if (int16_t(r0) < int16_t(~r1))
 		m_core->m_r[REG_SR] |= UNSP_S;
-	if(value & 0x8000)
+	if (BIT(value, 15))
 		m_core->m_r[REG_SR] |= UNSP_N;
 	if((uint16_t)value == 0)
 		m_core->m_r[REG_SR] |= UNSP_Z;
-	if(value != (uint16_t)value)
+	if (BIT(value, 16))
 		m_core->m_r[REG_SR] |= UNSP_C;
 }
 
@@ -877,33 +877,37 @@ inline void unsp_device::execute_one(const uint16_t op)
 	switch (op0)
 	{
 		case 0x00: // Add
+		{
 			lres = r0 + r1;
 			if (opa != 7)
 				update_nzsc(lres, r0, r1);
 			break;
+		}
 		case 0x01: // Add w/ carry
-			lres = r0 + r1;
-			if(m_core->m_r[REG_SR] & UNSP_C)
-				lres++;
+		{
+			uint32_t c = (m_core->m_r[REG_SR] & UNSP_C) ? 1 : 0;
+			lres = r0 + r1 + c;
 			if (opa != 7)
 				update_nzsc(lres, r0, r1);
 			break;
+		}
 		case 0x02: // Subtract
-			lres = r0 + (uint16_t)(~r1) + 1;
+			lres = r0 + (uint16_t)(~r1) + uint32_t(1);
 			if (opa != 7)
-				update_nzsc(lres, r0, r1);
+				update_nzsc(lres, r0, ~r1);
 			break;
 		case 0x03: // Subtract w/ carry
-			lres = r0 + (uint16_t)(~r1);
-			if(m_core->m_r[REG_SR] & UNSP_C)
-				lres++;
+		{
+			uint32_t c = (m_core->m_r[REG_SR] & UNSP_C) ? 1 : 0;
+			lres = r0 + (uint16_t)(~r1) + c;
 			if (opa != 7)
-				update_nzsc(lres, r0, r1);
+				update_nzsc(lres, r0, ~r1);
 			break;
+		}
 		case 0x04: // Compare
-			lres = r0 + (uint16_t)(~r1) + 1;
+			lres = r0 + (uint16_t)(~r1) + uint32_t(1);
 			if (opa != 7)
-				update_nzsc(lres, r0, r1);
+				update_nzsc(lres, r0, ~r1);
 			return;
 		case 0x06: // Negate
 			lres = -r1;
diff --git a/src/devices/cpu/unsp/unspdrc.cpp b/src/devices/cpu/unsp/unspdrc.cpp
index eb010bd3a37..5ffd0bfe956 100644
--- a/src/devices/cpu/unsp/unspdrc.cpp
+++ b/src/devices/cpu/unsp/unspdrc.cpp
@@ -634,6 +634,7 @@ void unsp_device::generate_add_lpc(drcuml_block &block, int32_t offset)
 
 void unsp_device::generate_update_nzsc(drcuml_block &block)
 {
+	UML_XOR(block, I1, I1, 0x0000ffff);
 	UML_SEXT(block, I1, I1, SIZE_WORD);
 	UML_SEXT(block, I2, I2, SIZE_WORD);
 	UML_CMP(block, I2, I1);
@@ -644,9 +645,8 @@ void unsp_device::generate_update_nzsc(drcuml_block &block)
 	UML_SETc(block, uml::COND_NZ, I1);
 	UML_ROLINS(block, mem(&m_core->m_r[REG_SR]), I1, UNSP_N_SHIFT, UNSP_N);
 
-	UML_AND(block, I2, I3, 0x0000ffff);
-	UML_CMP(block, I3, I2);
-	UML_SETc(block, uml::COND_NE, I1);
+	UML_TEST(block, I3, 0x10000);
+	UML_SETc(block, uml::COND_NZ, I1);
 	UML_ROLINS(block, mem(&m_core->m_r[REG_SR]), I1, UNSP_C_SHIFT, UNSP_C);
 
 	UML_CMP(block, I2, 0);
diff --git a/src/mame/drivers/vii.cpp b/src/mame/drivers/vii.cpp
index ba586013476..ff2abd49970 100644
--- a/src/mame/drivers/vii.cpp
+++ b/src/mame/drivers/vii.cpp
@@ -1236,7 +1236,7 @@ CONS( 2008, jak_wall, 0, 0, walle, walle,  spg2xx_game_state, empty_init, "JAKKS
 CONS( 2005, jak_wwe,  0, 0, jakks_gkr,    jak_gkr,jakks_gkr_state, empty_init, "JAKKS Pacific Inc / HotGen Ltd",          "WWE (JAKKS Pacific TV Game, Game-Key Ready)",            MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS ) // WW (no game-keys released)
 CONS( 2005, jak_fan4, 0, 0, jakks_gkr,    jak_gkr,jakks_gkr_state, empty_init, "JAKKS Pacific Inc / Digital Eclipse",     "Fantastic Four (JAKKS Pacific TV Game, Game-Key Ready)", MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS ) // F4 (no game-keys released)
 CONS( 2005, jak_just, 0, 0, jakks_gkr,    jak_gkr,jakks_gkr_state, empty_init, "JAKKS Pacific Inc / Taniko",              "Justice League (JAKKS Pacific TV Game, Game-Key Ready)", MACHINE_NOT_WORKING | MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS ) // DC (no game-keys released)
-CONS( 2005, jak_dora, 0, 0, jakks_gkr_nk, jak_gkr,jakks_gkr_state, empty_init, "JAKKS Pacific Inc / Handheld Games",      "Dora the Explorer - Race To Play Park (JAKKS Pacific TV Game, Game-Key Ready)", MACHINE_NOT_WORKING | MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS ) // uses NK keys (same as Nicktoons & Spongebob) (3+ released)
+CONS( 2005, jak_dora, 0, 0, jakks_gkr_nk, jak_gkr,jakks_gkr_state, empty_init, "JAKKS Pacific Inc / Handheld Games",      "Dora the Explorer - Race To Play Park (JAKKS Pacific TV Game, Game-Key Ready)", MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS ) // uses NK keys (same as Nicktoons & Spongebob) (3+ released)
 CONS( 2005, jak_sdoo, 0, 0, jakks_gkr,    jak_gkr,jakks_gkr_state, empty_init, "JAKKS Pacific Inc / Jolliford Management","Scooby-Doo! and the Mystery of the Castle (JAKKS Pacific TV Game, Game-Key Ready)", MACHINE_NOT_WORKING | MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS ) //  SD (no game-keys released)
 CONS( 2005, jak_disf, 0, 0, jakks_gkr_dy, jak_gkr,jakks_gkr_state, empty_init, "JAKKS Pacific Inc / HotGen Ltd",          "Disney Friends (JAKKS Pacific TV Game, Game-Key Ready)", MACHINE_NOT_WORKING | MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS ) // uses DY keys (3 released)