diff --git a/BizHawk.Emulation/BizHawk.Emulation.csproj b/BizHawk.Emulation/BizHawk.Emulation.csproj
index 8395c1f06a..865f1c96d1 100644
--- a/BizHawk.Emulation/BizHawk.Emulation.csproj
+++ b/BizHawk.Emulation/BizHawk.Emulation.csproj
@@ -173,6 +173,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper242.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper078.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper046.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper243.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper246.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper60.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper61.cs" />
diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper225.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper225.cs
index 8dd19278eb..1150efbf4e 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper225.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper225.cs
@@ -38,7 +38,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 		CHR Setup:
 		---------------------------
 
-		$0000   $0400   $0800   $0C00   $1000   $1400   $1800   $1C00 
+					  $0000   $0400   $0800   $0C00   $1000   $1400   $1800   $1C00 
 					+---------------------------------------------------------------+
 		CHR Mode 0: |                             $8000                             |
 					+---------------------------------------------------------------+
@@ -58,6 +58,8 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 		bool prg_mode = false;
 		int chr_reg;
 		int prg_reg;
+		ByteBuffer eRAM = new ByteBuffer(4);
+		int chr_bank_mask_8k, prg_bank_mask_16k, prg_bank_mask_32k;
 
 		public override bool Configure(NES.EDetectionOrigin origin)
 		{
@@ -68,6 +70,9 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 				default:
 					return false;
 			}
+			chr_bank_mask_8k = Cart.chr_size / 8 - 1;
+			prg_bank_mask_16k = Cart.prg_size / 16 - 1;
+			prg_bank_mask_32k = Cart.prg_size / 32 - 1;
 
 			SetMirrorType(EMirrorType.Vertical);
 
@@ -79,13 +84,20 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			ser.Sync("prg_reg", ref prg_reg);
 			ser.Sync("chr_reg", ref chr_reg);
 			ser.Sync("prg_mode", ref prg_mode);
+			ser.Sync("eRAM", ref eRAM);
 			base.SyncState(ser);
 		}
 
+		public override void Dispose()
+		{
+			eRAM.Dispose();
+			base.Dispose();
+		}
+
 		public override void WritePRG(int addr, byte value)
 		{
+			addr += 0x8000;
 			prg_mode = addr.Bit(12);
-
 			if (addr.Bit(13))
 			{
 				SetMirrorType(EMirrorType.Horizontal);
@@ -94,6 +106,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			{
 				SetMirrorType(EMirrorType.Vertical);
 			}
+
 			int high = (addr & 0x4000) >> 8;
 			prg_reg = (addr >> 6) & 0x3F | high;
 			chr_reg = addr & 0x3F | high;
@@ -101,13 +114,14 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 
 		public override byte ReadPRG(int addr)
 		{
-			if (prg_mode)
+			if (prg_mode == false)
 			{
-				return ROM[((prg_reg >> 1) * 0x8000) + addr];
+				int bank = (prg_reg >> 1) & prg_bank_mask_32k;
+				return ROM[(bank * 0x8000) + addr];
 			}
 			else
 			{
-				return ROM[(prg_reg * 0x4000) + (addr & 0x3FFF)];
+				return ROM[((prg_reg & prg_bank_mask_16k) * 0x4000) + (addr & 0x3FFF)];
 			}
 		}
 
@@ -115,9 +129,29 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 		{
 			if (addr < 0x2000)
 			{
-				return VROM[(chr_reg * 0x2000) + addr];
+				return VROM[((chr_reg & chr_bank_mask_8k) * 0x2000) + addr];
 			}
 			return base.ReadPPU(addr);
 		}
+
+		public override void WriteEXP(int addr, byte value)
+		{
+			if (addr >= 0x1800)
+			{
+				eRAM[(addr & 0x07)] = (byte)(value & 0x0F);
+			}
+		}
+
+		public override byte ReadEXP(int addr)
+		{
+			if (addr >= 0x1800)
+			{
+				return eRAM[(addr & 0x07)];
+			}
+			else
+			{
+				return base.ReadEXP(addr);
+			}
+		}
 	}
 }