diff --git a/BizHawk.Client.EmuHawk/MainForm.Designer.cs b/BizHawk.Client.EmuHawk/MainForm.Designer.cs
index 399cedf8a9..5f47cb66d0 100644
--- a/BizHawk.Client.EmuHawk/MainForm.Designer.cs
+++ b/BizHawk.Client.EmuHawk/MainForm.Designer.cs
@@ -334,7 +334,8 @@
             this.ColecoSubMenu = new System.Windows.Forms.ToolStripMenuItem();
             this.ColecoControllerSettingsMenuItem = new System.Windows.Forms.ToolStripMenuItem();
             this.ColecoSkipBiosMenuItem = new System.Windows.Forms.ToolStripMenuItem();
-            this.N64SubMenu = new System.Windows.Forms.ToolStripMenuItem();
+			this.ColecoUseSGMMenuItem = new System.Windows.Forms.ToolStripMenuItem();
+			this.N64SubMenu = new System.Windows.Forms.ToolStripMenuItem();
             this.N64PluginSettingsMenuItem = new System.Windows.Forms.ToolStripMenuItem();
             this.N64ControllerSettingsMenuItem = new System.Windows.Forms.ToolStripMenuItem();
             this.toolStripSeparator23 = new System.Windows.Forms.ToolStripSeparator();
@@ -3034,7 +3035,8 @@
             this.ColecoSubMenu.DropDownItems.AddRange(new System.Windows.Forms.ToolStripItem[] {
             this.ColecoControllerSettingsMenuItem,
             this.toolStripSeparator35,
-            this.ColecoSkipBiosMenuItem});
+            this.ColecoSkipBiosMenuItem,
+			this.ColecoUseSGMMenuItem});
             this.ColecoSubMenu.Name = "ColecoSubMenu";
             this.ColecoSubMenu.Size = new System.Drawing.Size(56, 19);
             this.ColecoSubMenu.Text = "&Coleco";
@@ -3059,10 +3061,17 @@
             this.ColecoSkipBiosMenuItem.Size = new System.Drawing.Size(253, 22);
             this.ColecoSkipBiosMenuItem.Text = "&Skip BIOS intro (When Applicable)";
             this.ColecoSkipBiosMenuItem.Click += new System.EventHandler(this.ColecoSkipBiosMenuItem_Click);
-            // 
-            // N64SubMenu
-            // 
-            this.N64SubMenu.DropDownItems.AddRange(new System.Windows.Forms.ToolStripItem[] {
+			// 
+			// ColecoUseSGMMenuItem
+			// 
+			this.ColecoUseSGMMenuItem.Name = "ColecoUseSGMMenuItem";
+			this.ColecoUseSGMMenuItem.Size = new System.Drawing.Size(253, 22);
+			this.ColecoUseSGMMenuItem.Text = "&Use the Super Game Module";
+			this.ColecoUseSGMMenuItem.Click += new System.EventHandler(this.ColecoUseSGMMenuItem_Click);
+			// 
+			// N64SubMenu
+			// 
+			this.N64SubMenu.DropDownItems.AddRange(new System.Windows.Forms.ToolStripItem[] {
             this.N64PluginSettingsMenuItem,
             this.N64ControllerSettingsMenuItem,
             this.toolStripSeparator23,
@@ -4257,6 +4266,7 @@
 		private System.Windows.Forms.ToolStripSeparator toolStripSeparator28;
 		private System.Windows.Forms.ToolStripMenuItem ColecoSubMenu;
 		private System.Windows.Forms.ToolStripMenuItem ColecoSkipBiosMenuItem;
+		private System.Windows.Forms.ToolStripMenuItem ColecoUseSGMMenuItem;
 		private System.Windows.Forms.ToolStripMenuItem ColecoControllerSettingsMenuItem;
 		private System.Windows.Forms.ToolStripStatusLabel LedLightStatusLabel;
 		private System.Windows.Forms.ToolStripMenuItem GBASubMenu;
diff --git a/BizHawk.Client.EmuHawk/MainForm.Events.cs b/BizHawk.Client.EmuHawk/MainForm.Events.cs
index 5e5b535397..aafb6e0eaf 100644
--- a/BizHawk.Client.EmuHawk/MainForm.Events.cs
+++ b/BizHawk.Client.EmuHawk/MainForm.Events.cs
@@ -2206,6 +2206,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var ss = ((ColecoVision)Emulator).GetSyncSettings();
 			ColecoSkipBiosMenuItem.Checked = ss.SkipBiosIntro;
+			ColecoUseSGMMenuItem.Checked = ss.UseSGM;
 			ColecoControllerSettingsMenuItem.Enabled = !Global.MovieSession.Movie.IsActive;
 		}
 
@@ -2216,6 +2217,13 @@ namespace BizHawk.Client.EmuHawk
 			PutCoreSyncSettings(ss);
 		}
 
+		private void ColecoUseSGMMenuItem_Click(object sender, EventArgs e)
+		{
+			var ss = ((ColecoVision)Emulator).GetSyncSettings();
+			ss.UseSGM ^= true;
+			PutCoreSyncSettings(ss);
+		}
+
 		private void ColecoControllerSettingsMenuItem_Click(object sender, EventArgs e)
 		{
 			new ColecoControllerSettings().ShowDialog();
diff --git a/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj b/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
index cd7fe103fc..1d9458f597 100644
--- a/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
+++ b/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
@@ -415,6 +415,7 @@
     <Compile Include="Consoles\Coleco\ColecoVision.ISoundProvider.cs">
       <DependentUpon>ColecoVision.cs</DependentUpon>
     </Compile>
+    <Compile Include="Consoles\Coleco\AY_3_8910.cs" />
     <Compile Include="Consoles\Coleco\TMS9918A.cs" />
     <Compile Include="Consoles\Coleco\ColecoControllerDeck.cs" />
     <Compile Include="Consoles\Coleco\ColecoControllers.cs" />
@@ -1361,4 +1362,4 @@
   <Target Name="AfterBuild">
   </Target>
   -->
-</Project>
+</Project>
\ No newline at end of file
diff --git a/BizHawk.Emulation.Cores/Consoles/Coleco/AY_3_8910.cs b/BizHawk.Emulation.Cores/Consoles/Coleco/AY_3_8910.cs
new file mode 100644
index 0000000000..efcf38b8f7
--- /dev/null
+++ b/BizHawk.Emulation.Cores/Consoles/Coleco/AY_3_8910.cs
@@ -0,0 +1,400 @@
+using System;
+
+using BizHawk.Common;
+using BizHawk.Common.NumberExtensions;
+using BizHawk.Emulation.Common;
+
+namespace BizHawk.Emulation.Cores.ColecoVision
+{
+	public sealed class AY_3_8910 : ISoundProvider
+	{
+		private readonly BlipBuffer _blip = new BlipBuffer(4096);
+		private short[] _sampleBuffer = new short[0];
+
+
+		public AY_3_8910()
+		{
+			_blip.SetRates(894866 / 4.0, 44100);
+			Reset();
+		}
+
+		public byte[] Register = new byte[16];
+
+		public byte port_sel;
+
+		public int total_clock; // TODO: what is this used for?
+
+		public void Reset()
+		{
+			clock_A = clock_B = clock_C = 0x1000;
+			noise_clock = 0x20;
+			port_sel = 0;
+
+			for (int i = 0; i < 16; i++)
+			{
+				Register[i] = 0x0000;
+			}
+			sync_psg_state();
+			DiscardSamples();
+		}
+
+		public void DiscardSamples()
+		{
+			_blip.Clear();
+			_sampleClock = 0;
+		}
+
+		public void GetSamplesAsync(short[] samples)
+		{
+			throw new NotSupportedException("Async is not available");
+		}
+
+		public bool CanProvideAsync => false;
+
+		public SyncSoundMode SyncMode => SyncSoundMode.Sync;
+
+		public void SetSyncMode(SyncSoundMode mode)
+		{
+			if (mode != SyncSoundMode.Sync)
+			{
+				throw new InvalidOperationException("Only Sync mode is supported.");
+			}
+		}
+
+		public void GetSamplesSync(out short[] samples, out int nsamp)
+		{
+			_blip.EndFrame((uint)_sampleClock);
+			_sampleClock = 0;
+
+			nsamp = _blip.SamplesAvailable();
+			int targetLength = nsamp * 2;
+			if (_sampleBuffer.Length != targetLength)
+			{
+				_sampleBuffer = new short[targetLength];
+			}
+
+			_blip.ReadSamplesLeft(_sampleBuffer, nsamp);
+			for (int i = 0; i < _sampleBuffer.Length; i += 2)
+			{
+				_sampleBuffer[i + 1] = _sampleBuffer[i];
+			}
+
+			samples = _sampleBuffer;
+		}
+
+		public void GetSamples(short[] samples)
+		{
+			throw new Exception();
+		}
+
+		private static readonly int[] VolumeTable =
+		{
+			0x0000, 0x0055, 0x0079, 0x00AB, 0x00F1, 0x0155, 0x01E3, 0x02AA,
+			0x03C5, 0x0555, 0x078B, 0x0AAB, 0x0F16, 0x1555, 0x1E2B, 0x2AAA
+		};
+
+		private int _sampleClock;
+		private int _latchedSample;
+
+		private int TotalExecutedCycles;
+		private int PendingCycles;
+		private int psg_clock;
+		private int sq_per_A, sq_per_B, sq_per_C;
+		private int clock_A, clock_B, clock_C;
+		private int vol_A, vol_B, vol_C;
+		private bool A_on, B_on, C_on;
+		private bool A_up, B_up, C_up;
+		private bool A_noise, B_noise, C_noise;
+
+		private int env_per;
+		private int env_clock;
+		private int env_shape;
+		private int env_E;
+		private int E_up_down;
+		private int env_vol_A, env_vol_B, env_vol_C;
+
+		private int noise_clock;
+		private int noise_per;
+		private int noise = 0x1;
+
+		public Func<byte, bool, byte> ReadMemory;
+		public Func<byte, byte, bool, bool> WriteMemory;
+
+		public void SyncState(Serializer ser)
+		{
+			ser.BeginSection("PSG");
+
+			ser.Sync("Register", ref Register, false);
+			ser.Sync("Toal_executed_cycles", ref TotalExecutedCycles);
+			ser.Sync("Pending_Cycles", ref PendingCycles);
+
+			ser.Sync("psg_clock", ref psg_clock);
+			ser.Sync("clock_A", ref clock_A);
+			ser.Sync("clock_B", ref clock_B);
+			ser.Sync("clock_C", ref clock_C);
+			ser.Sync("noise_clock", ref noise_clock);
+			ser.Sync("env_clock", ref env_clock);
+			ser.Sync("A_up", ref A_up);
+			ser.Sync("B_up", ref B_up);
+			ser.Sync("C_up", ref C_up);
+			ser.Sync("noise", ref noise);
+			ser.Sync("env_E", ref env_E);
+			ser.Sync("E_up_down", ref E_up_down);
+			ser.Sync("port_sel", ref port_sel);
+
+			sync_psg_state();
+
+			ser.EndSection();
+		}
+
+		public byte ReadPSG()
+		{
+			return Register[port_sel];
+		}
+
+		private void sync_psg_state()
+		{
+			sq_per_A = (Register[0] & 0xFF) | (((Register[4] & 0xF) << 8));
+			if (sq_per_A == 0)
+			{
+				sq_per_A = 0x1000;
+			}
+
+			sq_per_B = (Register[1] & 0xFF) | (((Register[5] & 0xF) << 8));
+			if (sq_per_B == 0)
+			{
+				sq_per_B = 0x1000;
+			}
+
+			sq_per_C = (Register[2] & 0xFF) | (((Register[6] & 0xF) << 8));
+			if (sq_per_C == 0)
+			{
+				sq_per_C = 0x1000;
+			}
+
+			env_per = (Register[3] & 0xFF) | (((Register[7] & 0xFF) << 8));
+			if (env_per == 0)
+			{
+				env_per = 0x10000;
+			}
+
+			env_per *= 2;
+
+			A_on = Register[8].Bit(0);
+			B_on = Register[8].Bit(1);
+			C_on = Register[8].Bit(2);
+			A_noise = Register[8].Bit(3);
+			B_noise = Register[8].Bit(4);
+			C_noise = Register[8].Bit(5);
+
+			noise_per = Register[9] & 0x1F;
+			if (noise_per == 0)
+			{
+				noise_per = 0x20;
+			}
+
+			var shape_select = Register[10] & 0xF;
+
+			if (shape_select < 4)
+				env_shape = 0;
+			else if (shape_select < 8)
+				env_shape = 1;
+			else
+				env_shape = 2 + (shape_select - 8);
+
+			vol_A = Register[11] & 0xF;
+			env_vol_A = (Register[11] >> 4) & 0x3;
+
+			vol_B = Register[12] & 0xF;
+			env_vol_B = (Register[12] >> 4) & 0x3;
+
+			vol_C = Register[13] & 0xF;
+			env_vol_C = (Register[13] >> 4) & 0x3;
+		}
+
+		public bool WritePSG(byte value)
+		{
+				value &= 0xFF;
+
+				if (port_sel == 4 || port_sel == 5 || port_sel == 6 || port_sel == 10)
+					value &= 0xF;
+
+				if (port_sel == 9)
+					value &= 0x1F;
+
+				if (port_sel == 11 || port_sel == 12 || port_sel == 13)
+					value &= 0x3F;
+
+				Register[port_sel] = value;
+
+				sync_psg_state();
+
+				if (port_sel == 10)
+				{
+					env_clock = env_per;
+
+					if (env_shape == 0 || env_shape == 2 || env_shape == 3 || env_shape == 4 || env_shape == 5)
+					{
+						env_E = 15;
+						E_up_down = -1;
+					}
+					else
+					{
+						env_E = 0;
+						E_up_down = 1;
+					}
+				}
+
+				return true;
+		}
+
+		public void generate_sound(int cycles_to_do)
+		{
+			// there are 4 cpu cycles for every psg cycle
+			bool sound_out_A;
+			bool sound_out_B;
+			bool sound_out_C;
+
+			for (int i = 0; i < cycles_to_do; i++)
+			{
+				psg_clock++;
+
+				if (psg_clock == 4)
+				{
+					psg_clock = 0;
+
+					total_clock++;
+
+					clock_A--;
+					clock_B--;
+					clock_C--;
+
+					noise_clock--;
+					env_clock--;
+
+					// clock noise
+					if (noise_clock == 0)
+					{
+						noise = (noise >> 1) ^ (noise.Bit(0) ? 0x10004 : 0);
+						noise_clock = noise_per;
+					}
+
+					if (env_clock == 0)
+					{
+						env_clock = env_per;
+
+						env_E += E_up_down;
+
+						if (env_E == 16 || env_E == -1)
+						{
+
+							// we just completed a period of the envelope, determine what to do now based on the envelope shape
+							if (env_shape == 0 || env_shape == 1 || env_shape == 3 || env_shape == 9)
+							{
+								E_up_down = 0;
+								env_E = 0;
+							}
+							else if (env_shape == 5 || env_shape == 7)
+							{
+								E_up_down = 0;
+								env_E = 15;
+							}
+							else if (env_shape == 4 || env_shape == 8)
+							{
+								if (env_E == 16)
+								{
+									env_E = 15;
+									E_up_down = -1;
+								}
+								else
+								{
+									env_E = 0;
+									E_up_down = 1;
+								}
+							}
+							else if (env_shape == 2)
+							{
+								env_E = 15;
+							}
+							else
+							{
+								env_E = 0;
+							}
+						}
+					}
+
+					if (clock_A == 0)
+					{
+						A_up = !A_up;
+						clock_A = sq_per_A;
+					}
+
+					if (clock_B == 0)
+					{
+						B_up = !B_up;
+						clock_B = sq_per_B;
+					}
+
+					if (clock_C == 0)
+					{
+						C_up = !C_up;
+						clock_C = sq_per_C;
+					}
+
+
+					sound_out_A = (noise.Bit(0) | A_noise) & (A_on | A_up);
+					sound_out_B = (noise.Bit(0) | B_noise) & (B_on | B_up);
+					sound_out_C = (noise.Bit(0) | C_noise) & (C_on | C_up);
+
+					// now calculate the volume of each channel and add them together
+					int v;
+
+					if (env_vol_A == 0)
+					{
+						v = (short)(sound_out_A ? VolumeTable[vol_A] : 0);
+					}
+					else
+					{
+						int shift_A = 3 - env_vol_A;
+						if (shift_A < 0)
+							shift_A = 0;
+						v = (short)(sound_out_A ? (VolumeTable[env_E] >> shift_A) : 0);
+					}
+
+					if (env_vol_B == 0)
+					{
+						v += (short)(sound_out_B ? VolumeTable[vol_B] : 0);
+
+					}
+					else
+					{
+						int shift_B = 3 - env_vol_B;
+						if (shift_B < 0)
+							shift_B = 0;
+						v += (short)(sound_out_B ? (VolumeTable[env_E] >> shift_B) : 0);
+					}
+
+					if (env_vol_C == 0)
+					{
+						v += (short)(sound_out_C ? VolumeTable[vol_C] : 0);
+					}
+					else
+					{
+						int shift_C = 3 - env_vol_C;
+						if (shift_C < 0)
+							shift_C = 0;
+						v += (short)(sound_out_C ? (VolumeTable[env_E] >> shift_C) : 0);
+					}
+
+					if (v != _latchedSample)
+					{
+						_blip.AddDelta((uint)_sampleClock, v - _latchedSample);
+						_latchedSample = v;
+					}
+
+					_sampleClock++;
+				}
+			}
+		}
+	}
+}
diff --git a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.IEmulator.cs b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.IEmulator.cs
index 22e67db446..cc4cfc8e56 100644
--- a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.IEmulator.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.IEmulator.cs
@@ -51,6 +51,14 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 			}
 		}
 
+		public bool use_SGM = false;
+		public bool is_MC = false;
+		public int MC_bank = 0;
+		public bool enable_SGM_high = false;
+		public bool enable_SGM_low = false;
+		public byte port_0x53, port_0x7F;
+
+
 		public int Frame => _frame;
 
 		public string SystemId => "Coleco";
diff --git a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.ISettable.cs b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.ISettable.cs
index b043990793..5dfee99534 100644
--- a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.ISettable.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.ISettable.cs
@@ -46,6 +46,7 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 		public class ColecoSyncSettings
 		{
 			public bool SkipBiosIntro { get; set; }
+			public bool UseSGM { get; set; }
 
 			private string _port1 = ColecoVisionControllerDeck.DefaultControllerName;
 			private string _port2 = ColecoVisionControllerDeck.DefaultControllerName;
diff --git a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.ISoundProvider.cs b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.ISoundProvider.cs
index dc0d7b7a77..93cff88b54 100644
--- a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.ISoundProvider.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.ISoundProvider.cs
@@ -5,6 +5,7 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 	public partial class ColecoVision
 	{
 		private SN76489 PSG;
+		private AY_3_8910 SGM_sound;
 		private readonly FakeSyncSound _fakeSyncSound; 
 	}
 }
diff --git a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.IStatable.cs b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.IStatable.cs
index d079fa50f4..313fa40f30 100644
--- a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.IStatable.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.IStatable.cs
@@ -55,7 +55,16 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 			ser.BeginSection("Coleco");		
 			_vdp.SyncState(ser);
 			PSG.SyncState(ser);
+			SGM_sound.SyncState(ser);
+			ser.Sync("UseSGM", ref use_SGM);
+			ser.Sync("is_MC", ref is_MC);
+			ser.Sync("EnableSGMhigh", ref enable_SGM_high);
+			ser.Sync("EnableSGMlow", ref enable_SGM_low);
+			ser.Sync("Port_0x53", ref port_0x53);
+			ser.Sync("Port_0x7F", ref port_0x7F);
 			ser.Sync("RAM", ref _ram, false);
+			ser.Sync("SGM_high_RAM", ref SGM_high_RAM, false);
+			ser.Sync("SGM_low_RAM", ref SGM_low_RAM, false);
 			ser.Sync("Frame", ref _frame);
 			ser.Sync("LagCount", ref _lagCount);
 			ser.Sync("IsLag", ref _isLag);
diff --git a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.cs b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.cs
index 070c8a2655..230cda9897 100644
--- a/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Coleco/ColecoVision.cs
@@ -1,6 +1,7 @@
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components;
 using BizHawk.Emulation.Cores.Components.Z80A;
+using System;
 
 namespace BizHawk.Emulation.Cores.ColecoVision
 {
@@ -36,6 +37,8 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 			_fakeSyncSound = new FakeSyncSound(PSG, 735);
 			ser.Register<ISoundProvider>(_fakeSyncSound);
 
+			SGM_sound = new AY_3_8910();
+
 			ControllerDeck = new ColecoVisionControllerDeck(_syncSettings.Port1, _syncSettings.Port2);
 
 			_vdp = new TMS9918A(_cpu);
@@ -56,6 +59,9 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 			_tracer.Header = _cpu.TraceHeader;
 			ser.Register<IDisassemblable>(_cpu);
 			ser.Register<ITraceable>(_tracer);
+
+			use_SGM = _syncSettings.UseSGM;
+			Console.WriteLine(use_SGM);
 		}
 
 		private readonly Z80A _cpu;
@@ -65,6 +71,9 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 
 		private byte[] _romData;
 		private byte[] _ram = new byte[1024];
+		public byte[] SGM_high_RAM = new byte[0x6000];
+		public byte[] SGM_low_RAM = new byte[0x2000];
+
 		private int _frame;
 		private IController _controller;
 
@@ -79,10 +88,22 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 
 		private void LoadRom(byte[] rom, bool skipbios)
 		{
-			_romData = new byte[0x8000];
-			for (int i = 0; i < 0x8000; i++)
+			if (rom.Length <= 32768)
 			{
-				_romData[i] = rom[i % rom.Length];
+				_romData = new byte[0x8000];
+				for (int i = 0; i < 0x8000; i++)
+				{
+					_romData[i] = rom[i % rom.Length];
+				}
+			}
+			else
+			{
+				// all original ColecoVision games had 32k or less of ROM
+				// so, if we have more then that, we must be using a MegaCart mapper
+				is_MC = true;
+
+				_romData = rom;
+
 			}
 
 			// hack to skip colecovision title screen
@@ -117,6 +138,29 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 				return ReadController2();
 			}
 
+			if (use_SGM)
+			{
+				if (port == 0x50)
+				{
+					return SGM_sound.port_sel;
+				}
+
+				if (port == 0x52)
+				{
+					return SGM_sound.Register[SGM_sound.port_sel];
+				}
+
+				if (port == 0x53)
+				{
+					return port_0x53;
+				}
+
+				if (port == 0x7F)
+				{
+					return port_0x7F;
+				}
+			}
+
 			return 0xFF;
 		}
 
@@ -154,6 +198,48 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 			{
 				PSG.WritePsgData(value, _cpu.TotalExecutedCycles);
 			}
+
+			if (use_SGM)
+			{
+				if (port == 0x50)
+				{
+					SGM_sound.port_sel = (byte)(value & 0xF);
+				}
+
+				if (port == 0x51)
+				{
+					SGM_sound.Register[SGM_sound.port_sel] = value;
+				}
+
+				if (port == 0x53)
+				{
+					if ((value & 1) > 0)
+					{
+						enable_SGM_high = true;
+					}
+					else
+					{
+						// NOTE: the documentation states that you shouldn't turn RAM back off once enabling it
+						// so we won't do anything here
+					}
+
+					port_0x53 = value;
+				}
+
+				if (port == 0x7F)
+				{
+					if (value == 0xF)
+					{
+						enable_SGM_low = false;
+					}
+					else if (value == 0xD)
+					{
+						enable_SGM_low = true;
+					}
+
+					port_0x7F = value;
+				}
+			}
 		}
 
 		private byte ReadController1()
@@ -198,17 +284,57 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 		{
 			if (addr >= 0x8000)
 			{
-				return _romData[addr & 0x7FFF];
+				if (!is_MC)
+				{
+					return _romData[addr & 0x7FFF];
+				}
+				else
+				{
+					// reading from 0xFFC0 to 0xFFFF triggers bank switching
+					// I don't know if it happens before or after the read though
+
+					if (addr >= 0xFFC0)
+					{
+						MC_bank = (addr - 0xFFC0) & (_romData.Length / 0x4000 - 1);
+					}
+					
+					// the first 16K of the map is always the last 16k of the ROM
+					if (addr < 0xC000)
+					{
+						return _romData[_romData.Length - 0x4000 + (addr - 0x8000)];
+					}
+					else
+					{
+						return _romData[MC_bank * 0x4000 + (addr - 0xC000)];
+					}
+				}
 			}
 
-			if (addr >= 0x6000)
+			if (!enable_SGM_high)
 			{
-				return _ram[addr & 1023];
+				if (addr >= 0x6000)
+				{
+					return _ram[addr & 1023];
+				}
+			}
+			else
+			{
+				if (addr >= 0x2000)
+				{
+					return SGM_high_RAM[addr - 0x2000];
+				}
 			}
 
 			if (addr < 0x2000)
 			{
-				return _biosRom[addr];
+				if (!enable_SGM_low)
+				{
+					return _biosRom[addr];
+				}
+				else
+				{
+					return SGM_low_RAM[addr];
+				}
 			}
 
 			////Console.WriteLine("Unhandled read at {0:X4}", addr);
@@ -217,11 +343,28 @@ namespace BizHawk.Emulation.Cores.ColecoVision
 
 		private void WriteMemory(ushort addr, byte value)
 		{
-			if (addr >= 0x6000 && addr < 0x8000)
+			if (!enable_SGM_high)
 			{
-				_ram[addr & 1023] = value;
+				if (addr >= 0x6000 && addr < 0x8000)
+				{
+					_ram[addr & 1023] = value;
+				}
+			}
+			else
+			{
+				if (addr >= 0x2000 && addr < 0x8000)
+				{
+					SGM_high_RAM[addr - 0x2000] = value;
+				}
 			}
 
+			if (addr < 0x2000)
+			{
+				if (enable_SGM_low)
+				{
+					SGM_low_RAM[addr] = value;
+				}
+			}
 			////Console.WriteLine("Unhandled write at {0:X4}:{1:X2}", addr, value);
 		}