diff --git a/src/devices/cpu/ks0164/ks0164.cpp b/src/devices/cpu/ks0164/ks0164.cpp
index de36d230dfc..966d037d1a9 100644
--- a/src/devices/cpu/ks0164/ks0164.cpp
+++ b/src/devices/cpu/ks0164/ks0164.cpp
@@ -287,7 +287,7 @@ void ks0164_cpu_device::execute_run()
 			// ALU functions with other register
 			// 10ff frrr Ssss w100
 			u16 rv = m_r[(opcode >> 4) & 7];
-			u16 v = opcode & 0x0004 ? rv : opcode & 0x0080 ? s8(rv) : u8(rv);
+			u16 v = opcode & 0x0008 ? rv : opcode & 0x0080 ? s8(rv) : u8(rv);
 
 			do_alu(opcode, v);
 			break;
@@ -298,7 +298,7 @@ void ks0164_cpu_device::execute_run()
 			// 10ff frrr S... w101
 			u16 rv = m_program_cache->read_word(m_r[R_PC]);
 			m_r[R_PC] += 2;
-			u16 v = opcode & 0x0004 ? rv : opcode & 0x0080 ? s8(rv) : u8(rv);
+			u16 v = opcode & 0x0008 ? rv : opcode & 0x0080 ? s8(rv) : u8(rv);
 
 			do_alu(opcode, v);
 			break;
@@ -308,7 +308,7 @@ void ks0164_cpu_device::execute_run()
 			// ALU functions from memory indexed
 			// 10ff frrr Ssss w110
 			u16 a = m_r[(opcode >> 4) & 7];
-			u16 v = opcode & 0x0004 ? m_program->read_word(a) : opcode & 0x0080 ? s8(m_program->read_byte(a)) : u8(m_program->read_byte(a));
+			u16 v = opcode & 0x0008 ? m_program->read_word(a) : opcode & 0x0080 ? s8(m_program->read_byte(a)) : u8(m_program->read_byte(a));
 			m_icount -= 2;
 
 			do_alu(opcode, v);
@@ -320,7 +320,7 @@ void ks0164_cpu_device::execute_run()
 			// 10ff frrr Ssss w111
 			u16 a = m_r[(opcode >> 4) & 7] + m_program_cache->read_word(m_r[R_PC]);
 			m_r[R_PC] += 2;
-			u16 v = opcode & 0x0004 ? m_program->read_word(a) : opcode & 0x0080 ? s8(m_program->read_byte(a)) : u8(m_program->read_byte(a));
+			u16 v = opcode & 0x0008 ? m_program->read_word(a) : opcode & 0x0080 ? s8(m_program->read_byte(a)) : u8(m_program->read_byte(a));
 			m_icount -= 2;
 
 			do_alu(opcode, v);
diff --git a/src/devices/sound/ks0164.cpp b/src/devices/sound/ks0164.cpp
index a7877338ba1..56e116c5c21 100644
--- a/src/devices/sound/ks0164.cpp
+++ b/src/devices/sound/ks0164.cpp
@@ -63,6 +63,8 @@ void ks0164_device::device_reset()
 	memset(m_sregs, 0, sizeof(m_sregs));
 	m_unk60 = 0;
 	m_voice_select = 0;
+	m_irqen_76 = 0;
+	m_irqen_77 = 0;
 }
 
 u16 ks0164_device::vec_r(offs_t offset, u16 mem_mask)
@@ -128,6 +130,28 @@ void ks0164_device::voice_w(offs_t offset, u16 data, u16 mem_mask)
 	logerror("voice %02x.%02x = %04x (%04x)\n", m_voice_select & 0x1f, offset, m_sregs[m_voice_select & 0x1f][offset], m_cpu->pc());
 }
 
+u8 ks0164_device::irqen_76_r()
+{
+	return m_irqen_76;
+}
+
+void ks0164_device::irqen_76_w(u8 data)
+{
+	m_irqen_76 = data;
+	logerror("irqen_76 = %02x (%04x)\n", m_irqen_76, m_cpu->pc());
+}
+
+u8 ks0164_device::irqen_77_r()
+{
+	return m_irqen_77;
+}
+
+void ks0164_device::irqen_77_w(u8 data)
+{
+	m_irqen_77 = data;
+	logerror("irqen_77 = %02x (%04x)\n", m_irqen_77, m_cpu->pc());
+}
+
 u8 ks0164_device::unk60_r()
 {
 	return m_unk60;
@@ -160,6 +184,9 @@ void ks0164_device::cpu_map(address_map &map)
 	map(0x0062, 0x0063).rw(FUNC(ks0164_device::bank1_select_r), FUNC(ks0164_device::bank1_select_w));
 	map(0x0064, 0x0065).rw(FUNC(ks0164_device::bank2_select_r), FUNC(ks0164_device::bank2_select_w));
 
+	map(0x0076, 0x0076).rw(FUNC(ks0164_device::irqen_76_r), FUNC(ks0164_device::irqen_76_w));
+	map(0x0077, 0x0077).rw(FUNC(ks0164_device::irqen_77_r), FUNC(ks0164_device::irqen_77_w));
+
 	map(0x0080, 0x3fff).r(FUNC(ks0164_device::rom_r));
 	map(0x4000, 0x7fff).rw(FUNC(ks0164_device::bank1_r), FUNC(ks0164_device::bank1_w));
 	map(0x8000, 0xbfff).rw(FUNC(ks0164_device::bank2_r), FUNC(ks0164_device::bank2_w));
diff --git a/src/devices/sound/ks0164.h b/src/devices/sound/ks0164.h
index 399a0e8f39a..a1367df125e 100644
--- a/src/devices/sound/ks0164.h
+++ b/src/devices/sound/ks0164.h
@@ -41,6 +41,7 @@ private:
 
 	u8 m_unk60;
 	u8 m_voice_select;
+	u8 m_irqen_76, m_irqen_77;
 
 	void cpu_map(address_map &map);
 
@@ -55,6 +56,10 @@ private:
 	u16 bank2_select_r();
 	void bank2_select_w(offs_t, u16 data, u16 mem_mask);
 
+	u8 irqen_76_r();
+	void irqen_76_w(u8 data);
+	u8 irqen_77_r();
+	void irqen_77_w(u8 data);
 	u8 unk60_r();
 	void unk60_w(u8 data);
 	u8 voice_select_r();