diff --git a/BizHawk.Emulation.Common/Base Implementations/MemoryDomainImpls.cs b/BizHawk.Emulation.Common/Base Implementations/MemoryDomainImpls.cs
index be932755cf..ede698f122 100644
--- a/BizHawk.Emulation.Common/Base Implementations/MemoryDomainImpls.cs	
+++ b/BizHawk.Emulation.Common/Base Implementations/MemoryDomainImpls.cs	
@@ -1,4 +1,5 @@
-using System;
+using BizHawk.Common;
+using System;
 
 namespace BizHawk.Emulation.Common
 {
@@ -134,6 +135,60 @@ namespace BizHawk.Emulation.Common
 		}
 	}
 
+	public unsafe class MemoryDomainIntPtrMonitor : MemoryDomain
+	{
+		public IntPtr Data { get; set; }
+		private readonly IMonitor _monitor;
+
+		public override byte PeekByte(long addr)
+		{
+			if ((ulong)addr < (ulong)Size)
+			{
+				using (_monitor.EnterExit())
+				{
+					return ((byte*)Data)[addr];
+				}
+			}
+
+			throw new ArgumentOutOfRangeException(nameof(addr));
+		}
+
+		public override void PokeByte(long addr, byte val)
+		{
+			if (Writable)
+			{
+				if ((ulong)addr < (ulong)Size)
+				{
+					using (_monitor.EnterExit())
+					{
+						((byte*)Data)[addr] = val;
+					}
+				}
+				else
+				{
+					throw new ArgumentOutOfRangeException(nameof(addr));
+				}
+			}
+		}
+
+		public void SetSize(long size)
+		{
+			Size = size;
+		}
+
+		public MemoryDomainIntPtrMonitor(string name, Endian endian, IntPtr data, long size, bool writable, int wordSize,
+			IMonitor monitor)
+		{
+			Name = name;
+			EndianType = endian;
+			Data = data;
+			Size = size;
+			Writable = writable;
+			WordSize = wordSize;
+			_monitor = monitor;
+		}
+	}
+
 	public unsafe class MemoryDomainIntPtrSwap16 : MemoryDomain
 	{
 		public IntPtr Data { get; set; }
diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES9X/Snes9x.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES9X/Snes9x.cs
index cde42ac5fd..7767bceeef 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES9X/Snes9x.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES9X/Snes9x.cs
@@ -39,46 +39,38 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES9X
 				SpecialHeapSizeKB = 64
 			});
 
-			try
+			_core = BizInvoker.GetInvoker<LibSnes9x>(_exe, _exe);
+			if (!_core.biz_init())
 			{
-				_core = BizInvoker.GetInvoker<LibSnes9x>(_exe, _exe);
-				if (!_core.biz_init())
-				{
-					throw new InvalidOperationException("Init() failed");
-				}
-				if (!_core.biz_load_rom(rom, rom.Length))
-				{
-					throw new InvalidOperationException("LoadRom() failed");
-				}
-				_exe.Seal();
-
-				if (_core.biz_is_ntsc())
-				{
-					Console.WriteLine("NTSC rom loaded");
-					VsyncNumerator = 21477272;
-					VsyncDenominator = 357366;
-				}
-				else
-				{
-					Console.WriteLine("PAL rom loaded");
-					VsyncNumerator = 21281370;
-					VsyncDenominator = 425568;
-				}
-
-				_nsampTarget = (int)Math.Round(44100.0 * VsyncDenominator / VsyncNumerator);
-				_nsampWarn = (int)Math.Round(1.05 * 44100.0 * VsyncDenominator / VsyncNumerator);
-
-				_syncSettings = syncSettings;
-				InitControllers();
-				PutSettings(settings);
-				InitMemoryDomains();
-				InitSaveram();
+				throw new InvalidOperationException("Init() failed");
 			}
-			catch
+			if (!_core.biz_load_rom(rom, rom.Length))
 			{
-				Dispose();
-				throw;
+				throw new InvalidOperationException("LoadRom() failed");
 			}
+			_exe.Seal();
+
+			if (_core.biz_is_ntsc())
+			{
+				Console.WriteLine("NTSC rom loaded");
+				VsyncNumerator = 21477272;
+				VsyncDenominator = 357366;
+			}
+			else
+			{
+				Console.WriteLine("PAL rom loaded");
+				VsyncNumerator = 21281370;
+				VsyncDenominator = 425568;
+			}
+
+			_nsampTarget = (int)Math.Round(44100.0 * VsyncDenominator / VsyncNumerator);
+			_nsampWarn = (int)Math.Round(1.05 * 44100.0 * VsyncDenominator / VsyncNumerator);
+
+			_syncSettings = syncSettings;
+			InitControllers();
+			PutSettings(settings);
+			InitMemoryDomains();
+			InitSaveram();
 		}
 
 		#region controller
@@ -319,8 +311,11 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES9X
 			LibSnes9x.frame_info frame = new LibSnes9x.frame_info();
 
 			_core.biz_run(frame, _inputState);
-			Blit(frame);
-			Sblit(frame);
+			using (_exe.EnterExit())
+			{
+				Blit(frame);
+				Sblit(frame);
+			}
 		}
 
 		public int Frame { get; private set; }
@@ -644,8 +639,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES9X
 				_core.biz_get_memory_area(index++, native);
 				if (native.ptr != IntPtr.Zero && native.size > 0)
 				{
-					domains.Add(new MemoryDomainIntPtr(s, MemoryDomain.Endian.Little,
-						native.ptr, native.size, true, 2));
+					domains.Add(new MemoryDomainIntPtrMonitor(s, MemoryDomain.Endian.Little,
+						native.ptr, native.size, true, 2, _exe));
 				}
 			}
 			(ServiceProvider as BasicServiceProvider).Register<IMemoryDomains>(new MemoryDomainList(domains)
@@ -678,27 +673,31 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES9X
 
 		public byte[] CloneSaveRam()
 		{
-			var ret = new byte[_saveramSize];
-			var offset = 0;
-			foreach (var area in _saveramMemoryAreas)
+			using (_exe.EnterExit())
 			{
-				Marshal.Copy(area.ptr, ret, offset, area.size);
-				offset += area.size;
+				var ret = new byte[_saveramSize];
+				var offset = 0;
+				foreach (var area in _saveramMemoryAreas)
+				{
+					Marshal.Copy(area.ptr, ret, offset, area.size);
+					offset += area.size;
+				}
+				return ret;
 			}
-
-			return ret;
 		}
 
 		public void StoreSaveRam(byte[] data)
 		{
-			if (data.Length != _saveramSize)
-				throw new InvalidOperationException("Saveram size mismatch");
-
-			var offset = 0;
-			foreach (var area in _saveramMemoryAreas)
+			using (_exe.EnterExit())
 			{
-				Marshal.Copy(data, offset, area.ptr, area.size);
-				offset += area.size;
+				if (data.Length != _saveramSize)
+					throw new InvalidOperationException("Saveram size mismatch");
+				var offset = 0;
+				foreach (var area in _saveramMemoryAreas)
+				{
+					Marshal.Copy(data, offset, area.ptr, area.size);
+					offset += area.size;
+				}
 			}
 		}
 
diff --git a/BizHawk.Emulation.Cores/Waterbox/PeRunner.cs b/BizHawk.Emulation.Cores/Waterbox/PeRunner.cs
index e0ad1159d7..e3de218abc 100644
--- a/BizHawk.Emulation.Cores/Waterbox/PeRunner.cs
+++ b/BizHawk.Emulation.Cores/Waterbox/PeRunner.cs
@@ -565,9 +565,8 @@ namespace BizHawk.Emulation.Cores.Waterbox
 		public PeRunner(PeRunnerOptions opt)
 		{
 			Initialize(_nextStart);
-			Enter();
-			try
-			{
+			using (this.EnterExit())
+			{ 
 				// load any predefined exports
 				_psx = new Psx(this);
 				_exports.Add("libpsxscl.so", BizExvoker.GetExvoker(_psx));
@@ -644,15 +643,6 @@ namespace BizHawk.Emulation.Cores.Waterbox
 					m.RunGlobalCtors();
 				}*/
 			}
-			catch
-			{
-				Dispose();
-				throw;
-			}
-			finally
-			{
-				Exit();
-			}
 		}
 
 		public IntPtr Resolve(string entryPoint)