diff --git a/Core/Bmc830425C4391T.h b/Core/Bmc830425C4391T.h
new file mode 100644
index 00000000..0d7e3590
--- /dev/null
+++ b/Core/Bmc830425C4391T.h
@@ -0,0 +1,55 @@
+#pragma once
+#include "stdafx.h"
+#include "BaseMapper.h"
+
+class Bmc830425C4391T : public BaseMapper
+{
+private:
+	uint8_t _innerReg;
+	uint8_t _outerReg;
+	uint8_t _prgMode;
+
+protected:
+	virtual uint16_t GetPRGPageSize() override { return 0x4000; }
+	virtual uint16_t GetCHRPageSize() override { return 0x2000; }
+
+	void InitMapper() override
+	{
+		_innerReg = 0;
+		_outerReg = 0;
+		_prgMode = 0;
+
+		SelectCHRPage(0, 0);
+		UpdateState();
+	}
+
+	void StreamState(bool saving) override
+	{
+		BaseMapper::StreamState(saving);
+		Stream(_innerReg, _outerReg, _prgMode);
+	}
+
+	void UpdateState()
+	{
+		if(_prgMode) {
+			//UNROM mode
+			SelectPRGPage(0, (_innerReg & 0x07) | (_outerReg << 3));
+			SelectPRGPage(1, 0x07 | (_outerReg << 3));
+		} else {
+			//UOROM mode
+			//FIXME: Mermaid game doesn't work
+			SelectPRGPage(0, _innerReg | (_outerReg << 3));
+			SelectPRGPage(1, 0x0F | (_outerReg << 3));
+		}
+	}
+
+	void WriteRegister(uint16_t addr, uint8_t value) override
+	{
+		_innerReg = value & 0x0F;
+		if((addr & 0xF0E0) == 0xF0E0) {
+			_outerReg = addr & 0x0F;
+			_prgMode = (addr >> 4) & 0x01;
+		}
+		UpdateState();
+	}
+};
diff --git a/Core/Core.vcxproj b/Core/Core.vcxproj
index 23c92ac5..725b9c78 100644
--- a/Core/Core.vcxproj
+++ b/Core/Core.vcxproj
@@ -522,6 +522,7 @@
     <ClInclude Include="Bmc80013B.h" />
     <ClInclude Include="Bmc8157.h" />
     <ClInclude Include="Bmc830118C.h" />
+    <ClInclude Include="Bmc830425C4391T.h" />
     <ClInclude Include="Bmc8in1.h" />
     <ClInclude Include="BmcGn45.h" />
     <ClInclude Include="BmcHpxx.h" />
diff --git a/Core/Core.vcxproj.filters b/Core/Core.vcxproj.filters
index e1dc1eaa..92bc2d60 100644
--- a/Core/Core.vcxproj.filters
+++ b/Core/Core.vcxproj.filters
@@ -1456,6 +1456,9 @@
     <ClInclude Include="ResetTxrom.h">
       <Filter>Nes\Mappers\Unif</Filter>
     </ClInclude>
+    <ClInclude Include="Bmc830425C4391T.h">
+      <Filter>Nes\Mappers\Unif</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="stdafx.cpp">
diff --git a/Core/MapperFactory.cpp b/Core/MapperFactory.cpp
index 57c459a3..dce8e262 100644
--- a/Core/MapperFactory.cpp
+++ b/Core/MapperFactory.cpp
@@ -32,6 +32,7 @@
 #include "Bmc80013B.h"
 #include "Bmc810544CA1.h"
 #include "Bmc830118C.h"
+#include "Bmc830425C4391T.h"
 #include "Bmc8in1.h"
 #include "BmcG146.h"
 #include "BmcGn45.h"
@@ -586,7 +587,7 @@ BaseMapper* MapperFactory::GetMapperFromID(RomData &romData)
 		case 315: break; //830134C
 		//316-318
 		case 319: return new Hp898f();
-		case 320: break; //830425C-4391T
+		case 320: return new Bmc830425C4391T();
 		//321
 		case 322: break; //K-3033
 		case 323: break; //FARID_SLROM_8-IN-1
diff --git a/Core/UnifLoader.cpp b/Core/UnifLoader.cpp
index 0a5349f8..aef5b8f0 100644
--- a/Core/UnifLoader.cpp
+++ b/Core/UnifLoader.cpp
@@ -17,6 +17,7 @@ std::unordered_map<string, int> UnifLoader::_boardMappings = std::unordered_map<
 	{ "70in1", 236 },
 	{ "70in1B", 236 },
 	{ "810544-C-A1", 261 },
+	{ "830425C-4391T", 320 },
 	{ "8157", 301 },
 	{ "8237", 215 },
 	{ "8237A", UnifBoards::Unl8237A },