diff --git a/BizHawk.Client.EmuHawk/MainForm.cs b/BizHawk.Client.EmuHawk/MainForm.cs
index f9ee25dd1e..5f425f7a1c 100644
--- a/BizHawk.Client.EmuHawk/MainForm.cs
+++ b/BizHawk.Client.EmuHawk/MainForm.cs
@@ -836,7 +836,7 @@ namespace BizHawk.Client.EmuHawk
 		public void RebootCore()
 		{
 			var ioa = OpenAdvancedSerializer.ParseWithLegacy(CurrentlyOpenRom);
-			if (ioa is IOpenAdvancedLibretro)
+			if (ioa is OpenAdvanced_LibretroNoGame)
 				LoadRom("", CurrentlyOpenRomArgs);
 			else
 				LoadRom(ioa.SimplePath, CurrentlyOpenRomArgs);
diff --git a/BizHawk.Common/Win32Hacks.cs b/BizHawk.Common/Win32Hacks.cs
index 5405076205..88313cb295 100644
--- a/BizHawk.Common/Win32Hacks.cs
+++ b/BizHawk.Common/Win32Hacks.cs
@@ -4,6 +4,75 @@ using System.Runtime.InteropServices;
 
 namespace BizHawk.Common
 {
+	public static class Win32PInvokes
+	{
+		[DllImport("kernel32.dll")]
+		[return: MarshalAs(UnmanagedType.Bool)]
+		public static extern bool IsProcessorFeaturePresent(ProcessorFeature processorFeature);
+
+		public enum ProcessorFeature : uint
+		{
+			/// <summary>
+			/// On a Pentium, a floating-point precision error can occur in rare circumstances
+			/// </summary>
+			FloatingPointPrecisionErrata = 0,
+			/// <summary>
+			/// Floating-point operations are emulated using a software emulator.
+			/// This function returns a nonzero value if floating-point operations are emulated; otherwise, it returns zero.
+			/// </summary>
+			FloatingPointEmulated = 1,
+			/// <summary>
+			/// The atomic compare and exchange operation (cmpxchg) is available
+			/// </summary>
+			CompareExchangeDouble = 2,
+			/// <summary>
+			/// The MMX instruction set is available
+			/// </summary>
+			InstructionsMMXAvailable = 3,
+			/// <summary>
+			/// The SSE instruction set is available
+			/// </summary>
+			InstructionsXMMIAvailable = 6,
+			/// <summary>
+			/// The 3D-Now instruction set is available.
+			/// </summary>
+			Instruction3DNowAvailable = 7,
+			/// <summary>
+			/// The RDTSC instruction is available
+			/// </summary>
+			InstructionRDTSCAvailable = 8,
+			/// <summary>
+			/// The processor is PAE-enabled
+			/// </summary>
+			PAEEnabled = 9,
+			/// <summary>
+			/// The SSE2 instruction set is available
+			/// </summary>
+			InstructionsXMMI64Available = 10,
+			/// <summary>
+			/// Data execution prevention is enabled. (This feature is not supported until Windows XP SP2 and Windows Server 2003 SP1)
+			/// </summary>
+			NXEnabled = 12,
+			/// <summary>
+			/// The SSE3 instruction set is available. (This feature is not supported until Windows Vista)
+			/// </summary>
+			InstructionsSSE3Available = 13,
+			/// <summary>
+			/// The atomic compare and exchange 128-bit operation (cmpxchg16b) is available. (This feature is not supported until Windows Vista)
+			/// </summary>
+			CompareExchange128 = 14,
+			/// <summary>
+			/// The atomic compare 64 and exchange 128-bit operation (cmp8xchg16) is available (This feature is not supported until Windows Vista.)
+			/// </summary>
+			Compare64Exchange128 = 15,
+			/// <summary>
+			/// TBD
+			/// </summary>
+			ChannelsEnabled = 16,
+		}
+
+	}
+
 	//largely from https://raw.githubusercontent.com/noserati/tpl/master/ThreadAffinityTaskScheduler.cs (MIT license)
 	public static class Win32ThreadHacks
 	{
diff --git a/BizHawk.Emulation.Cores/LibRetro.cs b/BizHawk.Emulation.Cores/LibRetro.cs
index 124dc3cc5e..392a5d482a 100644
--- a/BizHawk.Emulation.Cores/LibRetro.cs
+++ b/BizHawk.Emulation.Cores/LibRetro.cs
@@ -263,6 +263,29 @@ namespace BizHawk.Emulation.Cores
 			SCROLLLOCK = 64
 		};
 
+		[Flags]
+		public enum RETRO_SIMD
+		{
+			SSE = (1 << 0),
+			SSE2 = (1 << 1),
+			VMX = (1 << 2),
+			VMX128 = (1 << 3),
+			AVX = (1 << 4),
+			NEON = (1 << 5),
+			SSE3 = (1 << 6),
+			SSSE3 = (1 << 7),
+			MMX = (1 << 8),
+			MMXEXT = (1 << 9),
+			SSE4 = (1 << 10),
+			SSE42 = (1 << 11),
+			AVX2 = (1 << 12),
+			VFPU = (1 << 13),
+			PS = (1 << 14),
+			AES = (1 << 15),
+			VFPV3 = (1 << 16),
+			VFPV4 = (1 << 17),
+		}
+
 		public enum RETRO_ENVIRONMENT
 		{
 			SET_ROTATION = 1,
@@ -371,6 +394,46 @@ namespace BizHawk.Emulation.Cores
 			public string meta;
 		}
 
+		//untested
+		public struct retro_perf_counter
+		{
+			public string ident;
+			public ulong start;
+			public ulong total;
+			public ulong call_cnt;
+
+			[MarshalAs(UnmanagedType.U1)]
+			public bool registered;
+		};
+
+		//perf callbacks
+		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+		public delegate long retro_perf_get_time_usec_t();
+		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+		public delegate long retro_perf_get_counter_t();
+		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+		public delegate ulong retro_get_cpu_features_t();
+		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+		public delegate void retro_perf_log_t();
+		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+		public delegate void retro_perf_register_t(ref retro_perf_counter counter);
+		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+		public delegate void retro_perf_start_t(ref retro_perf_counter counter);
+		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+		public delegate void retro_perf_stop_t(ref retro_perf_counter counter);
+
+		//for GET_PERF_INTERFACE
+		public struct retro_perf_callback
+		{
+			public retro_perf_get_time_usec_t get_time_usec;
+			public retro_get_cpu_features_t get_cpu_features;
+			public retro_perf_get_counter_t get_perf_counter;
+			public retro_perf_register_t perf_register;
+			public retro_perf_start_t perf_start;
+			public retro_perf_stop_t perf_stop;
+			public retro_perf_log_t perf_log;
+		}
+
 		#region callback prototypes
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		[return:MarshalAs(UnmanagedType.U1)]
diff --git a/BizHawk.Emulation.Cores/LibRetroEmulator.cs b/BizHawk.Emulation.Cores/LibRetroEmulator.cs
index 5e4e181787..c93e37827b 100644
--- a/BizHawk.Emulation.Cores/LibRetroEmulator.cs
+++ b/BizHawk.Emulation.Cores/LibRetroEmulator.cs
@@ -114,6 +114,8 @@ namespace BizHawk.Emulation.Cores
 				case LibRetro.RETRO_ENVIRONMENT.SET_PERFORMANCE_LEVEL:
 					return false;
 				case LibRetro.RETRO_ENVIRONMENT.GET_SYSTEM_DIRECTORY:
+					//please write an example of a core that crashes without this (fmsx malfunctions..)
+					//"this is optional, but many cores will silently malfunction without it as they can't load their firmware files"
 					//an alternative (alongside where the saverams and such will go?)
 					//*((IntPtr*)data.ToPointer()) = unmanagedResources.StringToHGlobalAnsi(CoreComm.CoreFileProvider.GetGameBasePath());
 					*((IntPtr*)data.ToPointer()) = SystemDirectoryAtom;
@@ -188,15 +190,18 @@ namespace BizHawk.Emulation.Cores
 				case LibRetro.RETRO_ENVIRONMENT.GET_LOG_INTERFACE:
 					return false;
 				case LibRetro.RETRO_ENVIRONMENT.GET_PERF_INTERFACE:
-					return false;
+					//some builds of fmsx core crash without this set
+					Marshal.StructureToPtr(retro_perf_callback, data, false);
+					return true;
 				case LibRetro.RETRO_ENVIRONMENT.GET_LOCATION_INTERFACE:
 					return false;
 				case LibRetro.RETRO_ENVIRONMENT.GET_CORE_ASSETS_DIRECTORY:
 					return false;
 				case LibRetro.RETRO_ENVIRONMENT.GET_SAVE_DIRECTORY:
+					//supposedly optional like everything else here, but without it ?? crashes (please write which case)
 					//this will suffice for now. if we find evidence later it's needed we can stash a string with 
 					//unmanagedResources and CoreFileProvider
-					*((IntPtr*)data.ToPointer()) = IntPtr.Zero; 
+					//*((IntPtr*)data.ToPointer()) = IntPtr.Zero; 
 					return false;
 				case LibRetro.RETRO_ENVIRONMENT.SET_CONTROLLER_INFO:
 					return true;
@@ -265,6 +270,8 @@ namespace BizHawk.Emulation.Cores
 		LibRetro.retro_input_poll_t retro_input_poll_cb;
 		LibRetro.retro_input_state_t retro_input_state_cb;
 
+		LibRetro.retro_perf_callback retro_perf_callback = new LibRetro.retro_perf_callback();
+
 		#endregion
 
 		private LibRetro retro;
@@ -292,7 +299,7 @@ namespace BizHawk.Emulation.Cores
 			ServiceProvider = new BasicServiceProvider(this);
 
 			_SyncSettings = new SyncSettings();
-
+		
 			retro_environment_cb = new LibRetro.retro_environment_t(retro_environment);
 			retro_video_refresh_cb = new LibRetro.retro_video_refresh_t(retro_video_refresh);
 			retro_audio_sample_cb = new LibRetro.retro_audio_sample_t(retro_audio_sample);
@@ -300,6 +307,21 @@ namespace BizHawk.Emulation.Cores
 			retro_input_poll_cb = new LibRetro.retro_input_poll_t(retro_input_poll);
 			retro_input_state_cb = new LibRetro.retro_input_state_t(retro_input_state);
 
+			//no way (need new mechanism) to check for SSSE3, MMXEXT, SSE4, SSE42
+			retro_perf_callback.get_cpu_features = new LibRetro.retro_get_cpu_features_t(() => (ulong)(
+					(Win32PInvokes.IsProcessorFeaturePresent(Win32PInvokes.ProcessorFeature.InstructionsXMMIAvailable) ? LibRetro.RETRO_SIMD.SSE : 0) |
+					(Win32PInvokes.IsProcessorFeaturePresent(Win32PInvokes.ProcessorFeature.InstructionsXMMI64Available) ? LibRetro.RETRO_SIMD.SSE2 : 0) |
+					(Win32PInvokes.IsProcessorFeaturePresent(Win32PInvokes.ProcessorFeature.InstructionsSSE3Available) ? LibRetro.RETRO_SIMD.SSE3 : 0) |
+					(Win32PInvokes.IsProcessorFeaturePresent(Win32PInvokes.ProcessorFeature.InstructionsMMXAvailable) ? LibRetro.RETRO_SIMD.MMX : 0)
+				) );
+			retro_perf_callback.get_perf_counter = new LibRetro.retro_perf_get_counter_t(() => System.Diagnostics.Stopwatch.GetTimestamp());
+			retro_perf_callback.get_time_usec = new LibRetro.retro_perf_get_time_usec_t(() => DateTime.Now.Ticks / 10);
+			retro_perf_callback.perf_log = new LibRetro.retro_perf_log_t( () => {} );
+			retro_perf_callback.perf_register = new LibRetro.retro_perf_register_t((ref LibRetro.retro_perf_counter counter) => { });
+			retro_perf_callback.perf_start = new LibRetro.retro_perf_start_t((ref LibRetro.retro_perf_counter counter) => { });
+			retro_perf_callback.perf_stop = new LibRetro.retro_perf_stop_t((ref LibRetro.retro_perf_counter counter) => { });
+
+
 			retro = new LibRetro(modulename);
 			try
 			{