diff --git a/BizHawk.Emulation/BizHawk.Emulation.csproj b/BizHawk.Emulation/BizHawk.Emulation.csproj
index 492263d848..62ee186e36 100644
--- a/BizHawk.Emulation/BizHawk.Emulation.csproj
+++ b/BizHawk.Emulation/BizHawk.Emulation.csproj
@@ -114,6 +114,7 @@
     <Compile Include="Consoles\GB\Input.cs" />
     <Compile Include="Consoles\GB\MemoryMap.cs" />
     <Compile Include="Consoles\GB\GB.cs" />
+    <Compile Include="Consoles\Intellivision\Cartridge.cs" />
     <Compile Include="Consoles\Intellivision\Intellicart.cs" />
     <Compile Include="Consoles\Intellivision\Intellivision.cs" />
     <Compile Include="Consoles\Intellivision\MemoryMap.cs" />
diff --git a/BizHawk.Emulation/CPUs/CP1610/CP1610.cs b/BizHawk.Emulation/CPUs/CP1610/CP1610.cs
index e647723e13..14aa393b4b 100644
--- a/BizHawk.Emulation/CPUs/CP1610/CP1610.cs
+++ b/BizHawk.Emulation/CPUs/CP1610/CP1610.cs
@@ -14,7 +14,7 @@ namespace BizHawk.Emulation.CPUs.CP1610
 		public int PendingCycles;
 
 		public Func<ushort, ushort> ReadMemory;
-		public Action<ushort, ushort> WriteMemory;
+		public Func<ushort, ushort, bool> WriteMemory;
 
 		private static bool logging = true;
 		private static StreamWriter log;
diff --git a/BizHawk.Emulation/Consoles/Intellivision/Cartridge.cs b/BizHawk.Emulation/Consoles/Intellivision/Cartridge.cs
new file mode 100644
index 0000000000..bb33de0fb8
--- /dev/null
+++ b/BizHawk.Emulation/Consoles/Intellivision/Cartridge.cs
@@ -0,0 +1,219 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Intellivision
+{
+	public sealed class Cartridge : ICart
+	{
+		private ushort[] Data = new ushort[56320];
+
+		public int Parse(byte[] Rom)
+		{
+			// TODO: Actually parse the ROM.
+			return 1;
+		}
+
+		public ushort? Read(ushort addr)
+		{
+			// TODO: Check if address is RAM / ROM.
+			switch (addr & 0xF000)
+			{
+				case 0x0000:
+					if (addr <= 0x03FF)
+						break;
+					if (addr <= 0x04FF)
+						// OK on all but Intellivision 2.
+						return Data[addr & 0x00FF];
+					else if (addr <= 0x06FF)
+						return Data[addr & 0x02FF];
+					else if (addr <= 0x0CFF)
+						// OK if no Intellivoice.
+						return Data[addr & 0x08FF];
+					else
+						return Data[addr & 0x0BFF];
+				case 0x2000:
+					// OK if no ECS.
+					return Data[(addr & 0x0FFF) + 0x0C00];
+				case 0x4000:
+					if (addr <= 0x47FF)
+						// OK if no ECS.
+						return Data[(addr & 0x07FF) + 0x1C00];
+					else if (addr == 0x4800)
+						return Data[0x2400];
+					else
+						return Data[(addr & 0x0FFF) + 0x1C00];
+				case 0x5000:
+				case 0x6000:
+					if (addr <= 0x5014)
+						return Data[(addr & 0x0014) + 0x2C00];
+					else
+						return Data[(addr & 0x1FFF) + 0x2C00];
+				case 0x7000:
+					if (addr == 0x7000)
+						// OK if no ECS.
+						return Data[0x04C00];
+					else if (addr <= 0x77FF)
+						// OK if no ECS.
+						return Data[(addr & 0x07FF) + 0x4C00];
+					else
+						// OK if no ECS.
+						return Data[(addr & 0x0FFF) + 0x4C00];
+				case 0x8000:
+					// OK. Avoid STIC alias at $8000-$803F.
+					return Data[(addr & 0x0FFF) + 0x5C00];
+				case 0x9000:
+				case 0xA000:
+				case 0xB000:
+					if (addr <= 0xB7FF)
+						return Data[(addr & 0x27FF) + 0x6C00];
+					else
+						return Data[(addr & 0x2FFF) + 0x6C00];
+				case 0xC000:
+					// OK. Avoid STIC alias at $C000-$C03F.
+					return Data[(addr & 0x0FFF) + 0x9C00];
+				case 0xD000:
+					return Data[(addr & 0x0FFF) + 0xAC00];
+				case 0xE000:
+					// OK if no ECS.
+					return Data[(addr & 0x0FFF) + 0xBC00];
+				case 0xF000:
+					if (addr <= 0xF7FF)
+						return Data[(addr & 0x07FF) + 0xCC00];
+					else
+						return Data[(addr & 0x0FFF) + 0xCC00];
+			}
+			return null;
+		}
+
+		public bool Write(ushort addr, ushort value)
+		{
+			// TODO: Check if address is RAM / ROM.
+			switch (addr & 0xF000)
+			{
+				case 0x0000:
+					if (addr <= 0x03FF)
+						break;
+					if (addr <= 0x04FF)
+					{
+						// OK on all but Intellivision 2.
+						Data[addr & 0x00FF] = value;
+						return true;
+					}
+					else if (addr <= 0x06FF)
+					{
+						Data[addr & 0x02FF] = value;
+						return true;
+					}
+					else if (addr <= 0x0CFF)
+					{
+						// OK if no Intellivoice.
+						Data[addr & 0x08FF] = value;
+						return true;
+					}
+					else
+					{
+						Data[addr & 0x0BFF] = value;
+						return true;
+					}
+				case 0x2000:
+					// OK if no ECS.
+					Data[(addr & 0x0FFF) + 0x0C00] = value;
+					return true;
+				case 0x4000:
+					if (addr <= 0x47FF)
+					{
+						// OK if no ECS.
+						Data[(addr & 0x07FF) + 0x1C00] = value;
+						return true;
+					}
+					else if (addr == 0x4800)
+					{
+						// OK only if boot ROM at $7000.
+						Data[0x2400] = value;
+						return true;
+					}
+					else
+					{
+						Data[(addr & 0x0FFF) + 0x1C00] = value;
+						return true;
+					}
+				case 0x5000:
+				case 0x6000:
+					if (addr <= 0x5014)
+					{
+						// OK only if boot ROM at $4800 or $7000.
+						Data[(addr & 0x0014) + 0x2C00] = value;
+						return true;
+					}
+					else
+					{
+						Data[(addr & 0x1FFF) + 0x2C00] = value;
+						return true;
+					}
+				case 0x7000:
+					if (addr == 0x7000)
+					{
+						// RAM at $7000 confuses EXEC boot sequence.
+						Data[0x04C00] = value;
+						return true;
+					}
+					else if (addr <= 0x77FF)
+					{
+						// OK if no ECS.
+						Data[(addr & 0x07FF) + 0x4C00] = value;
+						return true;
+					}
+					else
+					{
+						// Do not map RAM here due to GRAM alias.
+						Data[(addr & 0x0FFF) + 0x4C00] = value;
+						return true;
+					}
+				case 0x8000:
+					// OK. Avoid STIC alias at $8000-$803F.
+					Data[(addr & 0x0FFF) + 0x5C00] = value;
+					return true;
+				case 0x9000:
+				case 0xA000:
+				case 0xB000:
+					if (addr <= 0xB7FF)
+					{
+						Data[(addr & 0x27FF) + 0x6C00] = value;
+						return true;
+					}
+					else
+					{
+						// Do not map RAM here due to GRAM alias.
+						Data[(addr & 0x2FFF) + 0x6C00] = value;
+						return true;
+					}
+				case 0xC000:
+					// OK. Avoid STIC alias at $C000-$C03F.
+					Data[(addr & 0x0FFF) + 0x9C00] = value;
+					return true;
+				case 0xD000:
+					Data[(addr & 0x0FFF) + 0xAC00] = value;
+					return true;
+				case 0xE000:
+					// OK if no ECS.
+					Data[(addr & 0x0FFF) + 0xBC00] = value;
+					return true;
+				case 0xF000:
+					if (addr <= 0xF7FF)
+					{
+						Data[(addr & 0x07FF) + 0xCC00] = value;
+						return true;
+					}
+					else
+					{
+						// Do not map RAM here due to GRAM alias.
+						Data[(addr & 0x0FFF) + 0xCC00] = value;
+						return true;
+					}
+			}
+			return false;
+		}
+	}
+}
diff --git a/BizHawk.Emulation/Consoles/Intellivision/Intellicart.cs b/BizHawk.Emulation/Consoles/Intellivision/Intellicart.cs
index 50d6e109fd..b3d7d8c005 100644
--- a/BizHawk.Emulation/Consoles/Intellivision/Intellicart.cs
+++ b/BizHawk.Emulation/Consoles/Intellivision/Intellicart.cs
@@ -5,9 +5,9 @@ using System.Text;
 
 namespace BizHawk.Emulation.Consoles.Intellivision
 {
-	public sealed partial class Intellivision : ICart
+	public sealed class Intellicart : ICart
 	{
-		private ushort[] Intellicart = new ushort[65536];
+		private ushort[] Data = new ushort[65536];
 		private bool[][] MemoryAttributes = new bool[32][];
 		private ushort[][] FineAddresses = new ushort[32][];
 
@@ -52,12 +52,12 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 			return (ushort)((crc << 8) ^ CRC16_table[(crc >> 8) ^ data]);
 		}
 
-		public int Parse()
+		public int Parse(byte[] Rom)
 		{
 			int offset = 0;
 			// Check to see if the header is valid.
 			if (Rom[offset++] != 0xA8 || Rom[offset++] != (0xFF ^ Rom[offset++]))
-				throw new ArgumentException();
+				return -1;
 			ushort crc, expected;
 			// Parse for data segments.
 			for (int segment = 0; segment < Rom[1]; segment++)
@@ -69,9 +69,8 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 				crc = UpdateCRC16(crc, upper_end);
 				ushort start = (ushort)(upper_start << 8);
 				ushort end = (ushort)((upper_end << 8) | 0xFF);
-				// This range is invalid if it starts at a higher range than it ends.
 				if (end < start)
-					throw new ArgumentException();
+					throw new ArgumentException("Ranges can't start higher than they end.");
 				for (int addr = start; addr <= end; addr++)
 				{
 					ushort data;
@@ -80,12 +79,11 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 					crc = UpdateCRC16(crc, high);
 					crc = UpdateCRC16(crc, low);
 					data = (ushort)((high << 8) | low);
-					Intellicart[addr] = data;
+					Data[addr] = data;
 				}
 				expected = (ushort)((Rom[offset++] << 8) | Rom[offset++]);
-				// Check if there is an invalid CRC.
 				if (expected != crc)
-					throw new ArgumentException();
+					throw new ArgumentException("Invalid CRC.");
 			}
 			// Parse for memory attributes.
 			for (int range = 0; range < 32; range++)
@@ -117,9 +115,8 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 				int range_start = range * 2048;
 				ushort start = (ushort)((((Rom[index] >> 4) & 0x07) << 8) + range_start);
 				ushort end = (ushort)((((Rom[index]) & 0x07) << 8) + 0xFF + range_start);
-				// This range is invalid if it starts at a higher range than it ends.
 				if (end < start)
-					throw new ArgumentException();
+					throw new ArgumentException("Ranges can't start higher than they end.");
 				FineAddresses[range] = new ushort[2];
 				FineAddresses[range][0] = start;
 				FineAddresses[range][1] = end;
@@ -130,20 +127,20 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 			expected = (ushort)((Rom[offset++] << 8) | (Rom[offset++] & 0xFF));
 			// Check if there is an invalid CRC for the memory attributes / fine addresses.
 			if (expected != crc)
-				throw new ArgumentException();
+				throw new ArgumentException("Invalid CRC.");
 			return offset;
 		}
 
-		public ushort? ReadCart(ushort addr)
+		public ushort? Read(ushort addr)
 		{
 			int range = addr / 2048;
 			bool[] attributes = MemoryAttributes[range];
 			if (attributes[0] && addr >= FineAddresses[range][0] && addr <= FineAddresses[range][1])
-				return Intellicart[addr];
+				return Data[addr];
 			return null;
 		}
 
-		public bool WriteCart(ushort addr, ushort value)
+		public bool Write(ushort addr, ushort value)
 		{
 			int range = addr / 2048;
 			bool[] attributes = MemoryAttributes[range];
@@ -154,7 +151,7 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 					value &= 0xFF;
 				if (attributes[3])
 					throw new NotImplementedException("Bank-switched memory attribute not implemented.");
-				Intellicart[addr] = value;
+				Data[addr] = value;
 				return true;
 			}
 			return false;
diff --git a/BizHawk.Emulation/Consoles/Intellivision/Intellivision.cs b/BizHawk.Emulation/Consoles/Intellivision/Intellivision.cs
index b3a2b74c18..cec93f67de 100644
--- a/BizHawk.Emulation/Consoles/Intellivision/Intellivision.cs
+++ b/BizHawk.Emulation/Consoles/Intellivision/Intellivision.cs
@@ -11,6 +11,7 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 		GameInfo Game;
 
 		CP1610 Cpu;
+		ICart Cart;
 
 		public void LoadExecutive_ROM()
 		{
@@ -42,7 +43,12 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 			Game = game;
 			LoadExecutive_ROM();
 			LoadGraphics_ROM();
-			Parse();
+			Cart = new Intellicart();
+			if (Cart.Parse(Rom) == -1)
+			{
+				Cart = new Cartridge();
+				Cart.Parse(Rom);
+			}
 
 			Cpu = new CP1610();
 			Cpu.ReadMemory = ReadMemory;
diff --git a/BizHawk.Emulation/Consoles/Intellivision/MemoryMap.cs b/BizHawk.Emulation/Consoles/Intellivision/MemoryMap.cs
index 1319293351..da988a3d50 100644
--- a/BizHawk.Emulation/Consoles/Intellivision/MemoryMap.cs
+++ b/BizHawk.Emulation/Consoles/Intellivision/MemoryMap.cs
@@ -8,17 +8,6 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 	public sealed partial class Intellivision
 	{
 		private const string INVALID = "Invalid memory address.";
-		private const string UNOCCUPIED = "Unoccupied memory address.";
-		private const string UNOCCUPIED_CART_READ = "Unoccupied memory address available to cartridge not mapped as"
-			+ " readable.";
-		private const string UNOCCUPIED_CART_WRITE = "Unoccupied memory address available to cartridge not mapped as"
-			+ " writable.";
-		private const string READ_ONLY_STIC = "This STIC Register alias is read-only.";
-		private const string READ_ONLY_EXEC = "Executive ROM is read-only.";
-		private const string READ_ONLY_GROM = "Graphics ROM is read-only.";
-		private const string WRITE_ONLY_STIC = "This STIC Register alias is write-only.";
-		private const string GARBAGE = "Memory address contains a garbage value, perhaps only in the Intellivision II.";
-		private const string INTV2_EXEC = "Additional EXEC ROM, Intellivision II only.";
 
 		private ushort[] STIC_Registers = new ushort[64];
 		private ushort[] Scratchpad_RAM = new ushort[240];
@@ -27,12 +16,11 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 		private ushort[] Executive_ROM = new ushort[4096]; // TODO: Intellivision II support?
 		private ushort[] Graphics_ROM = new ushort[2048];
 		private ushort[] Graphics_RAM = new ushort[512];
-		private ushort[] Cartridge = new ushort[56320]; // TODO: Resize as cartridge mapping grows.
 
 		public ushort ReadMemory(ushort addr)
 		{
-			ushort? cart = ReadCart(addr);
-			ushort core;
+			ushort? cart = Cart.Read(addr);
+			ushort? core = null;
 			switch (addr & 0xF000)
 			{
 				case 0x0000:
@@ -43,7 +31,8 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 						// TODO: OK only during VBlank Period 2.
 						core = STIC_Registers[addr & 0x003F];
 					else if (addr <= 0x00FF)
-						throw new ArgumentException(UNOCCUPIED);
+						// Unoccupied.
+						break;
 					else if (addr <= 0x01EF)
 						core = Scratchpad_RAM[addr & 0x00EF];
 					else if (addr <= 0x01FF)
@@ -51,44 +40,15 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 					else if (addr <= 0x035F)
 						core = System_RAM[addr & 0x015F];
 					else if (addr <= 0x03FF)
-						// TODO: Intellivision II support?
-						throw new ArgumentException(GARBAGE);
+						// TODO: Garbage values for Intellivision II.
+						break;
 					else if (addr <= 0x04FF)
-						// TODO: Actually map cartridge (on all but Intellivision II) RAM / ROM to decide which path to take.
-						if (false)
-							// TODO: Intellivision II support?
-							throw new ArgumentException(INTV2_EXEC);
-						else
-							core = Cartridge[addr & 0x00FF];
-					else if (addr <= 0x06FF)
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[addr & 0x02FF];
-					else if (addr <= 0x0CFF)
-						// TODO: Actually map cartridge (only if no Intellivoice) RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[addr & 0x08FF];
-					else
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[addr & 0x0BFF];
+						// TODO: Additional EXEC ROM for Intellivision II.
+						break;
 					break;
 				case 0x1000:
 					core = Executive_ROM[addr & 0x0FFF];
 					break;
-				case 0x2000:
-					// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-					if (false)
-						throw new ArgumentException(UNOCCUPIED_CART_READ);
-					else
-						core = Cartridge[(addr & 0x0FFF) + 0x0C00];
-					break;
 				case 0x3000:
 					if (addr <= 0x37FF)
 						// TODO: OK only during VBlank Period 2.
@@ -109,667 +69,269 @@ namespace BizHawk.Emulation.Consoles.Intellivision
 				case 0x4000:
 					if (addr <= 0x403F)
 					{
-						// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-						if (true)
-						{
+						if (addr == 0x4021)
 							// TODO: OK only during VBlank Period 1.
-							if (addr == 0x4021)
-								// TODO: Switch into Color Stack mode.
-								core = STIC_Registers[0x0021];
-							else
-								throw new ArgumentException(WRITE_ONLY_STIC);
-						}
-						else
-							core = Cartridge[(addr & 0x003F) + 0x1C00];
-					}
-					else if (addr <= 0x47FF)
-					{
-						// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x07FF) + 0x1C00];
-					}
-					else if (addr == 0x4800)
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[0x2400];
-					}
-					else
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0FFF) + 0x1C00];
-					}
-					break;
-				case 0x5000:
-				case 0x6000:
-					if (addr <= 0x5014)
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0014) + 0x2C00];
-					}
-					else
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x1FFF) + 0x2C00];
+							// TODO: Switch into Color Stack mode.
+							core = STIC_Registers[0x0021];
 					}
 					break;
 				case 0x7000:
-					if (addr == 0x7000)
-					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (confuses EXEC boot sequence) / ROM to decide
-						 which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[0x04C00];
-					}
-					else if (addr <= 0x77FF)
-					{
-						// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x07FF) + 0x4C00];
-					}
+					if (addr <= 0x77FF)
+						// Available to cartridges.
+						break;
 					else if (addr <= 0x79FF)
-					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (Do not because of GRAM alias) / ROM to decide
-						 which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x09FF) + 0x4C00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else if (addr <= 0x7BFF)
-					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (Do not because of GRAM alias) / ROM to decide
-						 which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0BFF) + 0x4C00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else if (addr <= 0x7DFF)
-					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (Do not because of GRAM alias) / ROM to decide
-						 which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0DFF) + 0x4C00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else
-					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (Do not because of GRAM alias) / ROM to decide
-						 which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0FFF) + 0x4C00];
-					}
-					break;
+						// Write-only Graphics RAM.
+						break;
 				case 0x8000:
 					if (addr <= 0x803F)
 					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (true)
-						{
+						if (addr == 0x8021)
 							// TODO: OK only during VBlank Period 1.
-							if (addr == 0x8021)
-								// TODO: Switch into Color Stack mode.
-								core = STIC_Registers[0x0021];
-							else
-								throw new ArgumentException(WRITE_ONLY_STIC);
-						}
-						else
-							core = Cartridge[(addr & 0x003F) + 0x5C00];
-					}
-					else
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0FFF) + 0x5C00];
+							// TODO: Switch into Color Stack mode.
+							core = STIC_Registers[0x0021];
 					}
 					break;
-				case 0x9000:
-				case 0xA000:
 				case 0xB000:
 					if (addr <= 0xB7FF)
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x27FF) + 0x6C00];
-					}
+						// Available to cartridges.
+						break;
 					else if (addr <= 0xB9FF)
-					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x29FF) + 0x6C00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else if (addr <= 0xBBFF)
-					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x2BFF) + 0x6C00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else if (addr <= 0xBDFF)
-					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x2DFF) + 0x6C00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else
-					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x2FFF) + 0x6C00];
-					}
-					break;
+						// Write-only Graphics RAM.
+						break;
 				case 0xC000:
 					if (addr <= 0xC03F)
 					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (true)
-						{
+						if (addr == 0xC021)
 							// TODO: OK only during VBlank Period 1.
-							if (addr == 0xC021)
-								// TODO: Switch into Color Stack mode.
-								core = STIC_Registers[0x0021];
-							else
-								throw new ArgumentException(WRITE_ONLY_STIC);
-						}
-						else
-							core = Cartridge[(addr & 0x003F) + 0x9C00];
+							// TODO: Switch into Color Stack mode.
+							core = STIC_Registers[0x0021];
 					}
-					else
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0FFF) + 0x9C00];
-					}
-					break;
-				case 0xD000:
-					// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-					if (false)
-						throw new ArgumentException(UNOCCUPIED_CART_READ);
-					else
-						core = Cartridge[(addr & 0x0FFF) + 0xAC00];
-					break;
-				case 0xE000:
-					// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-					if (false)
-						throw new ArgumentException(UNOCCUPIED_CART_READ);
-					else
-						core = Cartridge[(addr & 0x0FFF) + 0xBC00];
 					break;
 				case 0xF000:
 					if (addr <= 0xF7FF)
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x07FF) + 0xCC00];
-					}
+						// Available to cartridges.
+						break;
 					else if (addr <= 0xF9FF)
-					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x09FF) + 0xCC00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else if (addr <= 0xFBFF)
-					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0BFF) + 0xCC00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else if (addr <= 0xFDFF)
-					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0DFF) + 0xCC00];
-					}
+						// Write-only Graphics RAM.
+						break;
 					else
-					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_READ);
-						else
-							core = Cartridge[(addr & 0x0FFF) + 0xCC00];
-					}
-					break;
-				default:
-					throw new ArgumentException(INVALID);
+						// Write-only Graphics RAM.
+						break;
 			}
-			/*
-			TODO: Fix Intellicart hook.
 			if (cart != null)
 				return (ushort)cart;
-			*/
-			return core;
+			else if (core == null)
+				throw new ArgumentException(INVALID);
+			return (ushort)core;
 		}
 
-		public void WriteMemory(ushort addr, ushort value)
+		public bool WriteMemory(ushort addr, ushort value)
 		{
-			WriteCart(addr, value);
+			bool cart = Cart.Write(addr, value);
 			switch (addr & 0xF000)
 			{
 				case 0x0000:
 					if (addr <= 0x003F)
+					{
+						// TODO: OK only during VBlank Period 1.
 						STIC_Registers[addr] = value;
+						return true;
+					}
 					else if (addr <= 0x007F)
-						throw new ArgumentException(READ_ONLY_STIC);
+						// Read-only STIC.
+						break;
 					else if (addr <= 0x00FF)
-						throw new ArgumentException(UNOCCUPIED);
+						// Unoccupied.
+						break;
 					else if (addr <= 0x01EF)
+					{
 						Scratchpad_RAM[addr & 0x00EF] = value;
+						return true;
+					}
 					else if (addr <= 0x01FF)
+					{
 						PSG_Registers[addr & 0x000F] = value;
+						return true;
+					}
 					else if (addr <= 0x035F)
+					{
 						System_RAM[addr & 0x015F] = value;
+						return true;
+					}
 					else if (addr <= 0x03FF)
-						// TODO: Intellivision II support?
-						throw new ArgumentException(GARBAGE);
+						// Read-only garbage values for Intellivision II.
+						break;
 					else if (addr <= 0x04FF)
-						// TODO: Actually map cartridge (on all but Intellivision II) RAM / ROM to decide which path to take.
-						if (false)
-							// TODO: Intellivision II support?
-							throw new ArgumentException(INTV2_EXEC);
-						else
-							Cartridge[addr & 0x00FF] = value;
-					else if (addr <= 0x06FF)
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[addr & 0x02FF] = value;
-					else if (addr <= 0x0CFF)
-						// TODO: Actually map cartridge (only if no Intellivoice) RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[addr & 0x08FF] = value;
-					else
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[addr & 0x0BFF] = value;
+						// Read-only additional EXEC ROM for Intellivision II.
+						break;
 					break;
 				case 0x1000:
-					throw new ArgumentException(READ_ONLY_EXEC);
-				case 0x2000:
-					// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-					if (false)
-						throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-					else
-						Cartridge[(addr & 0x0FFF) + 0x0C00] = value;
+					// Read-only Executive ROM.
 					break;
 				case 0x3000:
 					if (addr <= 0x37FF)
-						throw new ArgumentException(READ_ONLY_GROM);
+						// Read-only Graphics ROM.
+						break;
 					else if (addr <= 0x39FF)
+					{
 						// TODO: OK only during VBlank Period 2.
 						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
+					}
 					else if (addr <= 0x3BFF)
+					{
 						// TODO: OK only during VBlank Period 2.
 						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
+					}
 					else if (addr <= 0x3DFF)
+					{
 						// TODO: OK only during VBlank Period 2.
 						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
+					}
 					else
+					{
 						// TODO: OK only during VBlank Period 2.
 						Graphics_RAM[addr & 0x01FF] = value;
-					break;
+						return true;
+					}
 				case 0x4000:
 					if (addr <= 0x403F)
 					{
-						// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-						if (true)
-							// TODO: OK only during VBlank Period 1.
-							STIC_Registers[addr & 0x003F] = value;
-						else
-							Cartridge[(addr & 0x003F) + 0x1C00] = value;
-					}
-					else if (addr <= 0x47FF)
-					{
-						// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x07FF) + 0x1C00] = value;
-					}
-					else if (addr == 0x4800)
-					{
-						// TODO: Actually map cartridge (only if boot ROM at $7000) RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[0x2400] = value;
-					}
-					else
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x0FFF) + 0x1C00] = value;
-					}
-					break;
-				case 0x5000:
-				case 0x6000:
-					if (addr <= 0x5014)
-					{
-						/*
-						 TODO: Actually map (only if boot ROM at $4800 or $7000) cartridge RAM / ROM to decide which path to
-						 take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x0014) + 0x2C00] = value;
-					}
-					else
-					{
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x1FFF) + 0x2C00] = value;
+						// TODO: OK only during VBlank Period 1.
+						STIC_Registers[addr & 0x003F] = value;
+						return true;
 					}
 					break;
 				case 0x7000:
-					if (addr == 0x7000)
-					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (confuses EXEC boot sequence) / ROM to decide
-						 which path to take.
-						*/
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[0x04C00] = value;
-					}
-					else if (addr <= 0x77FF)
-					{
-						// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x07FF) + 0x4C00] = value;
-					}
+					if (addr <= 0x77FF)
+						// Available to cartridges.
+						break;
 					else if (addr <= 0x79FF)
 					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (Do not because of GRAM alias) / ROM to decide
-						 which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x09FF) + 0x4C00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else if (addr <= 0x7BFF)
 					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (Do not because of GRAM alias) / ROM to decide
-						 which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x0BFF) + 0x4C00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else if (addr <= 0x7DFF)
 					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (Do not because of GRAM alias) / ROM to decide
-						 which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x0DFF) + 0x4C00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else
 					{
-						/*
-						 TODO: Actually map cartridge (only if no ECS) RAM (Do not because of GRAM alias) / ROM to decide
-						 which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x0FFF) + 0x4C00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
-					break;
 				case 0x8000:
 					if (addr <= 0x803F)
 					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (true)
-							// TODO: OK only during VBlank Period 1.
-							STIC_Registers[addr & 0x003F] = value;
-						else
-							Cartridge[(addr & 0x003F) + 0x5C00] = value;
-					}
-					else
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x0FFF) + 0x5C00] = value;
+						// TODO: OK only during VBlank Period 1.
+						STIC_Registers[addr & 0x003F] = value;
+						return true;
 					}
 					break;
 				case 0x9000:
 				case 0xA000:
 				case 0xB000:
 					if (addr <= 0xB7FF)
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x27FF) + 0x6C00] = value;
-					}
+						// Available to cartridges.
+						break;
 					else if (addr <= 0xB9FF)
 					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x29FF) + 0x6C00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else if (addr <= 0xBBFF)
 					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x2BFF) + 0x6C00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else if (addr <= 0xBDFF)
 					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x2DFF) + 0x6C00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else
 					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x2FFF) + 0x6C00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
-					break;
 				case 0xC000:
 					if (addr <= 0x803F)
 					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (true)
-							// TODO: OK only during VBlank Period 1.
-							STIC_Registers[addr & 0x003F] = value;
-						else
-							Cartridge[(addr & 0x003F) + 0x9C00] = value;
+						// TODO: OK only during VBlank Period 1.
+						STIC_Registers[addr & 0x003F] = value;
+						return true;
 					}
-					else
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x0FFF) + 0x9C00] = value;
-					}
-					break;
-				case 0xD000:
-					// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-					if (false)
-						throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-					else
-						Cartridge[(addr & 0x0FFF) + 0xAC00] = value;
-					break;
-				case 0xE000:
-					// TODO: Actually map cartridge (only if no ECS) RAM / ROM to decide which path to take.
-					if (false)
-						throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-					else
-						Cartridge[(addr & 0x0FFF) + 0xBC00] = value;
 					break;
 				case 0xF000:
 					if (addr <= 0xF7FF)
-					{
-						// TODO: Actually map cartridge RAM / ROM to decide which path to take.
-						if (false)
-							throw new ArgumentException(UNOCCUPIED_CART_WRITE);
-						else
-							Cartridge[(addr & 0x07FF) + 0xCC00] = value;
-					}
+						// Available to cartridges.
+						break;
 					else if (addr <= 0xF9FF)
 					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x09FF) + 0xCC00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else if (addr <= 0xFBFF)
 					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x0BFF) + 0xCC00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else if (addr <= 0xFDFF)
 					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x0DFF) + 0xCC00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
 					else
 					{
-						/*
-						 TODO: Actually map cartridge RAM (Do not because of GRAM alias) / ROM to decide which path to take.
-						*/
-						if (true)
-							// TODO: OK only during VBlank Period 2.
-							Graphics_RAM[addr & 0x01FF] = value;
-						else
-							Cartridge[(addr & 0x0FFF) + 0xCC00] = value;
+						// TODO: OK only during VBlank Period 2.
+						Graphics_RAM[addr & 0x01FF] = value;
+						return true;
 					}
-					break;
-				default:
-					throw new ArgumentException(INVALID);
 			}
+			return cart;
 		}
 	}
 }
diff --git a/BizHawk.Emulation/Interfaces/ICart.cs b/BizHawk.Emulation/Interfaces/ICart.cs
index ab26cdaf10..6389742a35 100644
--- a/BizHawk.Emulation/Interfaces/ICart.cs
+++ b/BizHawk.Emulation/Interfaces/ICart.cs
@@ -7,7 +7,8 @@ namespace BizHawk
 {
 	public interface ICart
 	{
-		ushort? ReadCart(ushort addr);
-		bool WriteCart(ushort addr, ushort value);
+		int Parse(byte[] Rom);
+		ushort? Read(ushort addr);
+		bool Write(ushort addr, ushort value);
 	}
 }