diff --git a/BizHawk.Emulation/BizHawk.Emulation.csproj b/BizHawk.Emulation/BizHawk.Emulation.csproj
index 6dde8e636a..f9c68fe7ba 100644
--- a/BizHawk.Emulation/BizHawk.Emulation.csproj
+++ b/BizHawk.Emulation/BizHawk.Emulation.csproj
@@ -152,6 +152,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\JALECO_JF_19.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\JALECO_SS8806.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper015.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper027.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper038.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper040.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper045.cs" />
diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper027.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper027.cs
new file mode 100644
index 0000000000..bf4e2376f3
--- /dev/null
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper027.cs
@@ -0,0 +1,154 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	// World Hero (Unl)
+	// 8k banked prgrom, 1k banked chrrom, scanline counter
+	// tried to copy behavior from fceux, but it doesn't work
+	public class Mapper027 : NES.NESBoardBase
+	{
+		// state
+		int[] chr = new int[8];
+		int[] prg = new int[4];
+		int prglatch;
+		int irqlatch;
+		int irqstat;
+		int irqcount;
+
+		// config
+		int chr_mask;
+		int prg_mask;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER027":
+					break;
+				default:
+					return false;
+			}
+			AssertPrg(128);
+			AssertChr(512);
+			AssertVram(0);
+			AssertWram(0);
+			prg_mask = Cart.prg_size / 8 - 1;
+			chr_mask = Cart.chr_size / 1 - 1;
+			prg[3] = prg_mask;
+			return true;
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			return ROM[addr & 0x1fff | prg[addr >> 13] << 13];
+		}
+
+		public override byte ReadPPU(int addr)
+		{
+			if (addr < 0x2000)
+				return VROM[addr & 0x3ff | chr[addr >> 10] << 10];
+			else
+				return base.ReadPPU(addr);
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			addr &= 0xf00f;
+			//if (true)
+			//	Console.WriteLine("{0:x4}:{1:x2}", addr + 0x8000, value);
+			if (addr >= 0x3000 && addr <= 0x6003)
+			{
+				int regnum = (addr >> 12) + 1 & 3;
+				regnum = regnum << 1 | (addr & 2) >> 1;
+				if ((addr & 1) != 0)
+				{
+					chr[regnum] &= 0x00f;
+					chr[regnum] |= value << 4 & chr_mask;
+				}
+				else
+				{
+					chr[regnum] &= 0x1f0;
+					chr[regnum] |= value & 0xf & chr_mask;
+				}
+				return;
+			}
+
+			switch (addr)
+			{
+				case 0x0000:
+					prg[prglatch] = value & prg_mask;
+					break;
+				case 0x1000:
+					switch (value & 3)
+					{
+						case 0: SetMirrorType(EMirrorType.Vertical); break;
+						case 1: SetMirrorType(EMirrorType.Horizontal); break;
+						case 2: SetMirrorType(EMirrorType.OneScreenA); break;
+						case 3: SetMirrorType(EMirrorType.OneScreenB); break;
+					}
+					prglatch = value & 2; // in fceux, this runs because of a lack of case break.  bug?
+					break;
+				case 0x1002:
+					prglatch = value & 2;
+					break;
+				case 0x2000:
+					prg[1] = value & prg_mask;
+					break;
+				case 0x7000:
+					irqlatch &= 0xf0;
+					irqlatch |= value & 0x0f;
+					break;
+				case 0x7001:
+					irqlatch &= 0x0f;
+					irqlatch |= value << 4 & 0xf0;
+					break;
+				case 0x7002:
+					irqstat = value & 3;
+					if ((irqstat & 2) != 0)
+						irqcount = irqlatch - 1;
+					break;
+				case 0x7003:
+					irqstat = irqstat << 1 & 2 | irqstat & 1;
+					IRQSignal = false;
+					break;
+			}
+
+
+		}
+
+		// irq timing is entirely a guess; this bit improvised from ExROM
+		public override void ClockPPU()
+		{
+			if (NES.ppu.ppur.status.cycle != 336)
+				return;
+			if (!NES.ppu.reg_2001.PPUON)
+				return;
+
+			int sl = NES.ppu.ppur.status.sl + 1;
+
+			if (sl >= 241)
+				return;
+			hblanktrigger();
+		}
+
+		void hblanktrigger()
+		{
+			if ((irqstat & 2) != 0)
+			{
+				if (irqcount == 255)
+				{
+					IRQSignal = true;
+					irqcount = irqlatch + 1;
+					Console.WriteLine("Raise");
+				}
+				else
+					irqcount++;
+			}
+		}
+
+
+	}
+}