diff --git a/BizHawk.Emulation/BizHawk.Emulation.csproj b/BizHawk.Emulation/BizHawk.Emulation.csproj
index b112d37177..6f07a67f88 100644
--- a/BizHawk.Emulation/BizHawk.Emulation.csproj
+++ b/BizHawk.Emulation/BizHawk.Emulation.csproj
@@ -230,6 +230,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper090.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper091.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper101.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper103.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper107.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper108.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper116.cs" />
diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper103.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper103.cs
new file mode 100644
index 0000000000..1e9f80a314
--- /dev/null
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper103.cs
@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	// Doki Doki Panic (FDS port)
+	// "BTL 2708"
+	public class Mapper103 : NES.NESBoardBase
+	{
+		int prg;
+		bool romenable = false;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER103": // ines identification
+					Cart.wram_size = 16;
+					Cart.vram_size = 8;
+					AssertPrg(128);
+					break;
+				case "BTL-2708": // ??
+					break;
+				default:
+					return false;
+			}
+			SetMirrorType(EMirrorType.Vertical);
+			return true;
+		}
+
+		public override void WriteWRAM(int addr, byte value)
+		{
+			// writes always go to wram, even if rom is mapped in for read
+			WRAM[addr] = value;
+		}
+
+		public override byte ReadWRAM(int addr)
+		{
+			if (romenable)
+				return ROM[addr | prg << 13];
+			else
+				return WRAM[addr];
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			if (!romenable && addr >= 0x3800 && addr < 0x5800)
+				return WRAM[addr - 0x1800];
+			else
+				return ROM[addr | 0x18000];
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			if (addr >= 0x3800 && addr < 0x5800)
+				WRAM[addr - 0x1800] = value;
+			else
+			{
+				switch (addr & 0x7000)
+				{
+					case 0x0000:
+						prg = value & 15;
+						break;
+					case 0x6000:
+						SetMirrorType((value & 8) != 0 ? EMirrorType.Horizontal : EMirrorType.Vertical);
+						break;
+					case 0x7000:
+						romenable = (value & 16) != 0;
+						break;
+				}
+			}
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			base.SyncState(ser);
+			ser.Sync("romenable", ref romenable);
+			ser.Sync("prg", ref prg);
+		}
+
+	}
+}