diff --git a/src/BizHawk.Client.Common/RomLoader.cs b/src/BizHawk.Client.Common/RomLoader.cs
index eb4f1136e75..443504bce1d 100644
--- a/src/BizHawk.Client.Common/RomLoader.cs
+++ b/src/BizHawk.Client.Common/RomLoader.cs
@@ -482,12 +482,6 @@ private void LoadOther(
 						);
 						return;
 					}
-					static bool IsPreferredCoreSGB(Config config)
-						=> config.PreferredCores[VSystemID.Raw.GB] is CoreNames.Bsnes or CoreNames.Bsnes115 or CoreNames.SubBsnes115;
-					if (IsPreferredCoreSGB(_config))
-					{
-						game.System = VSystemID.Raw.SGB;
-					}
 					break;
 				case VSystemID.Raw.PSX when ext is ".bin":
 					const string FILE_EXT_CUE = ".cue";
@@ -853,11 +847,6 @@ private void DispatchErrorMessage(Exception ex, string system, string path)
 			{
 				DoLoadErrorCallback(ex.Message, system, path, Deterministic, LoadErrorType.MissingFirmware);
 			}
-			else if (ex is CGBNotSupportedException)
-			{
-				// failed to load SGB bios or game does not support SGB mode.
-				DoLoadErrorCallback("Failed to load a GB rom in SGB mode.  You might try disabling SGB Mode.", system);
-			}
 			else if (ex is NoAvailableCoreException)
 			{
 				// handle exceptions thrown by the new detected systems that BizHawk does not have cores for
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesCore.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesCore.cs
index d7b35ed2a49..eb00397ff9e 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesCore.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesCore.cs
@@ -17,8 +17,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 	[ServiceNotApplicable(new[] { typeof(IDriveLight) })]
 	public partial class BsnesCore : IEmulator, IDebuggable, IVideoProvider, ISaveRam, IStatable, IInputPollable, IRegionable, ISettable<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings>, IBSNESForGfxDebugger, IBoardInfo
 	{
+		[CoreConstructor(VSystemID.Raw.GB)]
+		[CoreConstructor(VSystemID.Raw.GBC)]
 		[CoreConstructor(VSystemID.Raw.Satellaview)]
-		[CoreConstructor(VSystemID.Raw.SGB)]
 		[CoreConstructor(VSystemID.Raw.SNES)]
 		public BsnesCore(CoreLoadParameters<SnesSettings, SnesSyncSettings> loadParameters) : this(loadParameters, false) { }
 		public BsnesCore(CoreLoadParameters<SnesSettings, SnesSyncSettings> loadParameters, bool subframe = false)
@@ -29,8 +30,8 @@ public BsnesCore(CoreLoadParameters<SnesSettings, SnesSyncSettings> loadParamete
 			this._romPath = Path.ChangeExtension(loadParameters.Roms[0].RomPath, null);
 			CoreComm = loadParameters.Comm;
 			_syncSettings = loadParameters.SyncSettings ?? new SnesSyncSettings();
-			SystemId = loadParameters.Game.System;
-			_isSGB = SystemId == VSystemID.Raw.SGB;
+			_isSGB = loadParameters.Game.System is VSystemID.Raw.GB or VSystemID.Raw.GBC;
+			SystemId = _isSGB ? VSystemID.Raw.SGB : loadParameters.Game.System;
 			_currentMsuTrack = new ProxiedFile();
 
 			byte[] sgbRomData = null;
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/SubBsnesCore.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/SubBsnesCore.cs
index f84cf5c905e..a66178219ca 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/SubBsnesCore.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/SubBsnesCore.cs
@@ -8,8 +8,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 	[ServiceNotApplicable(new[] { typeof(IDriveLight) })]
 	public class SubBsnesCore : IEmulator, ICycleTiming
 	{
+		[CoreConstructor(VSystemID.Raw.GB)]
+		[CoreConstructor(VSystemID.Raw.GBC)]
 		[CoreConstructor(VSystemID.Raw.Satellaview)]
-		[CoreConstructor(VSystemID.Raw.SGB)]
 		[CoreConstructor(VSystemID.Raw.SNES)]
 		public SubBsnesCore(CoreLoadParameters<BsnesCore.SnesSettings, BsnesCore.SnesSyncSettings> loadParameters)
 		{
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs
index 50a9eb2a338..bcee0d0cb01 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs
@@ -23,7 +23,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 	public unsafe partial class LibsnesCore : IEmulator, IVideoProvider, ISaveRam, IStatable, IInputPollable, IRegionable, ICodeDataLogger,
 		IDebuggable, ISettable<LibsnesCore.SnesSettings, LibsnesCore.SnesSyncSettings>, IBSNESForGfxDebugger
 	{
-		[CoreConstructor(VSystemID.Raw.SGB)]
+		[CoreConstructor(VSystemID.Raw.GB)]
+		[CoreConstructor(VSystemID.Raw.GBC)]
 		[CoreConstructor(VSystemID.Raw.SNES)]
 		public LibsnesCore(GameInfo game, byte[] rom, CoreComm comm,
 			LibsnesCore.SnesSettings settings, LibsnesCore.SnesSyncSettings syncSettings)
@@ -45,8 +46,9 @@ public LibsnesCore(GameInfo game, byte[] romData, byte[] xmlData, string baseRom
 			_game = game;
 			CoreComm = comm;
 			byte[] sgbRomData = null;
+			IsSGB = game.System is VSystemID.Raw.GB or VSystemID.Raw.GBC;
 
-			if (game.System == VSystemID.Raw.SGB)
+			if (IsSGB)
 			{
 				if ((romData[0x143] & 0xc0) == 0xc0)
 				{
@@ -110,9 +112,8 @@ public LibsnesCore(GameInfo game, byte[] romData, byte[] xmlData, string baseRom
 				romData = newData;
 			}
 
-			if (game.System == VSystemID.Raw.SGB)
+			if (IsSGB)
 			{
-				IsSGB = true;
 				SystemId = VSystemID.Raw.SNES;
 				ser.Register<IBoardInfo>(new SGBBoardInfo());