diff --git a/BizHawk.Emulation/BizHawk.Emulation.csproj b/BizHawk.Emulation/BizHawk.Emulation.csproj
index cc3b616974..048a84b5ab 100644
--- a/BizHawk.Emulation/BizHawk.Emulation.csproj
+++ b/BizHawk.Emulation/BizHawk.Emulation.csproj
@@ -156,8 +156,10 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper178.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper180.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper193.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper200.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper207.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper227.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper231.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper240.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper241.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper242.cs" />
diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper200.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper200.cs
new file mode 100644
index 0000000000..0e17077ead
--- /dev/null
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper200.cs
@@ -0,0 +1,109 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	class Mapper200 : NES.NESBoardBase
+	{
+		/*
+		Here are Disch's original notes:  
+		========================
+		=  Mapper 200          =
+		========================
+ 
+		Example Games:
+		--------------------------
+		1200-in-1
+		36-in-1
+ 
+ 
+		Registers:
+		---------------------------
+ 
+ 
+		$8000-FFFF:  A~[.... ....  .... MRRR]
+		M = Mirroring (0=Vert, 1=Horz)
+		R = PRG/CHR Reg
+ 
+ 
+		CHR Setup:
+		---------------------------
+ 
+		$0000   $0400   $0800   $0C00   $1000   $1400   $1800   $1C00 
+		+---------------------------------------------------------------+
+		|                             $8000                             |
+		+---------------------------------------------------------------+
+ 
+ 
+		PRG Setup:
+		---------------------------
+ 
+		$8000   $A000   $C000   $E000  
+		+---------------+---------------+
+		|     $8000     |     $8000     |
+		+---------------+---------------+
+		*/
+		int reg;
+		int prg_bank_mask_16k;
+		bool low;
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER200":
+				case "MAPPER229":
+					break;
+				default:
+					return false;
+			}
+
+			prg_bank_mask_16k = Cart.prg_size / 16 - 1;
+
+			return true;
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			ser.Sync("reg", ref reg);
+			base.SyncState(ser);
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			if (addr.Bit(3))
+			{
+				SetMirrorType(EMirrorType.Horizontal);
+			}
+			else
+			{
+				SetMirrorType(EMirrorType.Vertical);
+			}
+			reg = addr & 0x07;
+			low = addr.Bit(0);
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			if (addr < 0x4000)
+			{
+				return ROM[(reg * 0x4000) + addr];
+			}
+			else
+			{
+				int bank = reg >> 1;
+				return ROM[(bank * 0x4000) + addr];
+			}
+		}
+
+		public override byte ReadPPU(int addr)
+		{
+			if (addr < 0x2000)
+			{
+				return VROM[(reg * 0x2000) + addr];
+			}
+			return base.ReadPPU(addr);
+		}
+	}
+}
diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper231.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper231.cs
new file mode 100644
index 0000000000..a219e7ded2
--- /dev/null
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper231.cs
@@ -0,0 +1,97 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	class Mapper231 : NES.NESBoardBase
+	{
+		/*
+		* Here are Disch's original notes:  
+		========================
+		=  Mapper 231          =
+		========================
+ 
+		Example Game:
+		--------------------------
+		20-in-1
+ 
+ 
+ 
+		Registers:
+		---------------------------
+ 
+		$8000-FFFF:     A~[.... .... M.LP PPP.]
+		M = Mirroring (0=Vert, 1=Horz)
+		L = Low bit of PRG
+		P = High bits of PRG
+ 
+ 
+ 
+		PRG Setup:
+		---------------------------
+ 
+		Note that 'L' and 'P' bits make up the PRG reg, and the 'L' is the low bit.
+ 
+ 
+		$8000   $A000   $C000   $E000  
+		+---------------+---------------+
+		| $8000 AND $1E |     $8000     |
+		+---------------+---------------+
+		*/
+		public int reg;
+		public bool low;
+		public int prg_bank_mask_16k;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER231":
+					break;
+				default:
+					return false;
+			}
+
+			prg_bank_mask_16k = Cart.prg_size / 16 - 1;
+			return true;
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			ser.Sync("reg", ref reg);
+			ser.Sync("low", ref low);
+			base.SyncState(ser);
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			if (addr.Bit(7))
+			{
+				SetMirrorType(EMirrorType.Horizontal);
+			}
+			else
+			{
+				SetMirrorType(EMirrorType.Vertical);
+			}
+
+			low = addr.Bit(5);
+			reg = addr & 0x1E;
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			if (low)
+			{
+				int bank = ((reg >> 1) & 0x0F) & (prg_bank_mask_16k >> 1);
+				return ROM[(bank * 0x8000) + addr];
+			}
+			else
+			{
+				return ROM[((reg & prg_bank_mask_16k) * 0x4000) + addr];
+				
+			}
+		}
+	}
+}