diff --git a/BizHawk.Emulation/BizHawk.Emulation.csproj b/BizHawk.Emulation/BizHawk.Emulation.csproj
index c1c817d1ed..e528f878c1 100644
--- a/BizHawk.Emulation/BizHawk.Emulation.csproj
+++ b/BizHawk.Emulation/BizHawk.Emulation.csproj
@@ -83,6 +83,7 @@
     <Compile Include="Computers\Commodore64\C64.cs" />
     <Compile Include="Computers\Commodore64\Cartridges\Mapper0000.cs" />
     <Compile Include="Computers\Commodore64\C64.Input.cs" />
+    <Compile Include="Computers\Commodore64\Cartridges\Mapper0005.cs" />
     <Compile Include="Computers\Commodore64\Media\PRG.cs" />
     <Compile Include="Computers\Commodore64\Memory.cs" />
     <Compile Include="Computers\Commodore64\Cartridges\Cartridge.cs" />
diff --git a/BizHawk.Emulation/Computers/Commodore64/C64.Core.cs b/BizHawk.Emulation/Computers/Commodore64/C64.Core.cs
index e187b6b101..3dac6bc654 100644
--- a/BizHawk.Emulation/Computers/Commodore64/C64.Core.cs
+++ b/BizHawk.Emulation/Computers/Commodore64/C64.Core.cs
@@ -167,6 +167,10 @@ namespace BizHawk.Emulation.Computers.Commodore64
 
 		public void ExecutePhase1()
 		{
+			// sync cartridge lines (these can change)
+			pla.ExRom = cartPort.ExRom;
+			pla.Game = cartPort.Game;
+
 			cia0.ExecutePhase1();
 			cia1.ExecutePhase1();
 			sid.ExecutePhase1();
diff --git a/BizHawk.Emulation/Computers/Commodore64/Cartridges/Cartridge.cs b/BizHawk.Emulation/Computers/Commodore64/Cartridges/Cartridge.cs
index a6b122d8c0..72fdea9256 100644
--- a/BizHawk.Emulation/Computers/Commodore64/Cartridges/Cartridge.cs
+++ b/BizHawk.Emulation/Computers/Commodore64/Cartridges/Cartridge.cs
@@ -64,9 +64,12 @@ namespace BizHawk.Emulation.Computers.Commodore64.Cartridges
 				{
 					switch (mapper)
 					{
-						case 0:
+						case 0x0000:
 							result = new Mapper0000(chipData[0], exrom, game);
 							break;
+						case 0x0005:
+							result = new Mapper0005(chipAddress, chipBank, chipData);
+							break;
 						default:
 							break;
 					}
diff --git a/BizHawk.Emulation/Computers/Commodore64/Cartridges/Mapper0005.cs b/BizHawk.Emulation/Computers/Commodore64/Cartridges/Mapper0005.cs
new file mode 100644
index 0000000000..d20ed8c125
--- /dev/null
+++ b/BizHawk.Emulation/Computers/Commodore64/Cartridges/Mapper0005.cs
@@ -0,0 +1,130 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Computers.Commodore64.Cartridges
+{
+	public class Mapper0005 : Cartridge
+	{
+		private byte[][] banksA = new byte[0][]; //8000
+		private byte[][] banksB = new byte[0][]; //A000
+		private uint bankMask;
+		private uint bankNumber;
+		private byte[] currentBankA;
+		private byte[] currentBankB;
+		private byte[] dummyBank;
+
+		public Mapper0005(List<uint> newAddresses, List<uint> newBanks, List<byte[]> newData)
+		{
+			uint count = (uint)newAddresses.Count;
+
+			// build dummy bank
+			dummyBank = new byte[0x2000];
+			for (uint i = 0; i < 0x2000; i++)
+				dummyBank[i] = 0xFF; // todo: determine if this is correct
+
+			if (count == 64) //512k
+			{
+				pinGame = true;
+				pinExRom = false;
+				bankMask = 0x3F;
+				banksA = new byte[64][];
+			}
+			else if (count == 32) //256k
+			{
+				pinGame = false;
+				pinExRom = false;
+				bankMask = 0x0F;
+				banksA = new byte[16][];
+				banksB = new byte[16][];
+			}
+			else if (count == 16) //128k
+			{
+				pinGame = true;
+				pinExRom = false;
+				bankMask = 0x0F;
+				banksA = new byte[16][];
+			}
+			else if (count == 4) //32k
+			{
+				pinGame = true;
+				pinExRom = false;
+				bankMask = 0x03;
+				banksA = new byte[4][];
+			}
+			else
+			{
+				// we don't know what format this is...
+				throw new Exception("This looks like an Ocean cartridge but cannot be loaded...");
+			}
+
+			// for safety, initialize all banks to dummy
+			for (uint i = 0; i < banksA.Length; i++)
+				banksA[i] = dummyBank;
+			for (uint i = 0; i < banksB.Length; i++)
+				banksB[i] = dummyBank;
+
+			// now load in the banks
+			for (int i = 0; i < count; i++)
+			{
+				if (newAddresses[i] == 0x8000)
+				{
+					banksA[newBanks[i]] = newData[i];
+				}
+				else if (newAddresses[i] == 0xA000)
+				{
+					banksB[newBanks[i]] = newData[i];
+				}
+			}
+
+			BankSet(0);
+		}
+
+		private void BankSet(uint index)
+		{
+			bankNumber = index & bankMask;
+			if (!pinExRom)
+				currentBankA = banksA[bankNumber];
+			else
+				currentBankA = dummyBank;
+
+			if (!pinGame)
+				currentBankB = banksB[bankNumber];
+			else
+				currentBankB = dummyBank;
+		}
+
+		public override byte Peek8000(int addr)
+		{
+			return currentBankA[addr];
+		}
+
+		public override byte PeekA000(int addr)
+		{
+			return currentBankB[addr];
+		}
+
+		public override void PokeDE00(int addr, byte val)
+		{
+			if (addr == 0x00)
+				BankSet(val);
+		}
+
+		public override byte Read8000(ushort addr)
+		{
+			return currentBankA[addr];
+		}
+
+		public override byte ReadA000(ushort addr)
+		{
+			return currentBankB[addr];
+		}
+
+		public override void WriteDE00(ushort addr, byte val)
+		{
+			if (addr == 0x00)
+				BankSet(val);
+		}
+	}
+}
diff --git a/BizHawk.Emulation/Computers/Commodore64/MOS/MOSPLA.cs b/BizHawk.Emulation/Computers/Commodore64/MOS/MOSPLA.cs
index ac9108d65c..f619d906a3 100644
--- a/BizHawk.Emulation/Computers/Commodore64/MOS/MOSPLA.cs
+++ b/BizHawk.Emulation/Computers/Commodore64/MOS/MOSPLA.cs
@@ -557,6 +557,7 @@ namespace BizHawk.Emulation.Computers.Commodore64.MOS
 				case PLABank.None:
 					break;
 				case PLABank.RAM:
+					// RAM is written through anyway, don't do it here
 					break;
 				case PLABank.Sid:
 					chips.sid.Write(addr, val);