diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/AY38912.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/AY38912.cs
index 8dcde1e0ee..7443c43dd3 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/AY38912.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/AY38912.cs
@@ -60,6 +60,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             _tStatesPerSample = 79;
             _samplesPerFrame = _tStatesPerFrame / _tStatesPerSample;
             _AYCyclesPerFrame = _tStatesPerFrame / AY_SAMPLE_RATE;
+
+            _samples = new short[_samplesPerFrame * 2];
+            _nsamp = _samplesPerFrame;
         }
 
         #endregion
@@ -110,11 +113,11 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             
             // the stereo _samples buffer should already have been processed as a part of
             // ISoundProvider at the end of the last frame
-            _samples = new short[_samplesPerFrame * 2];
-            _nsamp = _samplesPerFrame;
+            //_samples = new short[_samplesPerFrame * 2];
+            //_nsamp = _samplesPerFrame;
             _sampleCounter = 0;
 
-            Init(44100, _tStatesPerFrame);
+            //Init(44100, _tStatesPerFrame);
         }
 
         public void EndFrame()
diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/Buzzer.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/Buzzer.cs
index d751189fae..04e5b53222 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/Buzzer.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/Buzzer.cs
@@ -123,6 +123,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// <param name="earPulse"></param>
         public void ProcessPulseValue(bool fromTape, bool earPulse)
         {
+            if (!_machine._renderSound)
+                return;
+
             if (!fromTape && _tapeMode)
             {
                 // tape mode is active but the pulse value came from an OUT instruction
diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/SpectrumBase.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/SpectrumBase.cs
index 28df887d46..444a22a46c 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/SpectrumBase.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/SpectrumBase.cs
@@ -76,25 +76,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// Holds the currently selected joysticks
         /// </summary>
         public virtual IJoystick[] JoystickCollection { get; set; }
-
-        /*
-        /// <summary>
-        /// Joystick device 1
-        /// </summary>
-        public virtual IJoystick Joystick1 { get; set; }
-
-        /// <summary>
-        /// Joystick device 2
-        /// </summary>
-        public virtual IJoystick Joystick2 { get; set; }
-
-        /// <summary>
-        /// Joystick device 3
-        /// </summary>
-        public virtual IJoystick Joystick3 { get; set; }
-
-    */
-
+        
         /// <summary>
         /// Signs whether the frame has ended
         /// </summary>
@@ -125,6 +107,12 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// </summary>
         public virtual int CurrentFrameCycle => CPU.TotalExecutedCycles - LastFrameStartCPUTick;
 
+        /// <summary>
+        /// Non-Deterministic bools
+        /// </summary>
+        public bool _render;
+        public bool _renderSound;
+
         /// <summary>
         /// Mask constants
         /// </summary>
@@ -138,14 +126,20 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// <summary>
         /// Executes a single frame
         /// </summary>
-        public virtual void ExecuteFrame()
+        public virtual void ExecuteFrame(bool render, bool renderSound)
         {
             InputRead = false;
+            _render = render;
+            _renderSound = renderSound;
 
             FrameCompleted = false;
-            BuzzerDevice.StartFrame();
-            if (AYDevice != null)
-                AYDevice.StartFrame();
+
+            if (_renderSound)
+            {
+                BuzzerDevice.StartFrame();
+                if (AYDevice != null)
+                    AYDevice.StartFrame();
+            }
 
             PollInput();
             
@@ -158,18 +152,22 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
                 CPU.ExecuteOne();
 
                 // update AY
-                if (AYDevice != null)
-                    AYDevice.UpdateSound(CurrentFrameCycle);
+                if (_renderSound)
+                {
+                    if (AYDevice != null)
+                        AYDevice.UpdateSound(CurrentFrameCycle);
+                }                
             }
             
             // we have reached the end of a frame
             LastFrameStartCPUTick = CPU.TotalExecutedCycles - OverFlow;
 
             // paint the buffer if needed
-            if (ULADevice.needsPaint)
+            if (ULADevice.needsPaint && _render)
                 ULADevice.UpdateScreenBuffer(ULADevice.FrameLength);
             
-            BuzzerDevice.EndFrame();            
+            if (_renderSound)
+                BuzzerDevice.EndFrame();            
 
             //TapeDevice.CPUFrameCompleted();
 
diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULABase.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULABase.cs
index 1604006525..e10bdd16c0 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULABase.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULABase.cs
@@ -315,7 +315,10 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             _machine.CPU.FlagI = true;
 
             // Signal the start of ULA processing
-            ULAUpdateStart();
+            if (_machine._render)
+                ULAUpdateStart();
+
+            CalcFlashCounter();
         }
 
         #endregion        
@@ -383,7 +386,13 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             screenByteCtr = DisplayStart;
             lastTState = actualULAStart;
             needsPaint = true;
+        }
 
+        /// <summary>
+        /// Flash processing
+        /// </summary>
+        public void CalcFlashCounter()
+        {
             flashCounter++;
 
             if (flashCounter > 15)
diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.IEmulator.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.IEmulator.cs
index c318876694..33bcc68276 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.IEmulator.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.IEmulator.cs
@@ -13,6 +13,15 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         {            
             _controller = controller;
 
+            bool ren = render;
+            bool renSound = renderSound;
+
+            if (DeterministicEmulation)
+            {
+                ren = true;
+                renSound = true;
+            }
+
             _isLag = true;
 
             if (_tracer.Enabled)
@@ -24,7 +33,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
                 _cpu.TraceCallback = null;
             }
 
-            _machine.ExecuteFrame();
+            _machine.ExecuteFrame(ren, renSound);
 
             if (_isLag)
             {
@@ -36,7 +45,13 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 
         public string SystemId => "ZXSpectrum";
 
-        public bool DeterministicEmulation => true;
+        private bool deterministicEmulation;
+        public bool DeterministicEmulation
+        {
+            get { return deterministicEmulation; }
+        }
+
+        //public bool DeterministicEmulation => true;
 
         public void ResetCounters()
         {
diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.ISettable.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.ISettable.cs
index 8ad6ab5b1e..059a2fcaa1 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.ISettable.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.ISettable.cs
@@ -72,6 +72,11 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 
         public class ZXSpectrumSyncSettings
         {
+            [DisplayName("Deterministic Emulation")]
+            [Description("If true, the core agrees to behave in a completely deterministic manner")]
+            [DefaultValue(true)]
+            public bool DeterministicEmulation { get; set; }
+
             [DisplayName("Spectrum model")]
             [Description("The model of spectrum to be emulated")]
             [DefaultValue(MachineType.ZXSpectrum48)]
diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.cs
index b8d3749514..4656ba6fa2 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.cs
@@ -50,6 +50,8 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             joysticks.Add(((ZXSpectrumSyncSettings)syncSettings as ZXSpectrumSyncSettings).JoystickType2);
             joysticks.Add(((ZXSpectrumSyncSettings)syncSettings as ZXSpectrumSyncSettings).JoystickType3);
 
+            deterministicEmulation = ((ZXSpectrumSyncSettings)syncSettings as ZXSpectrumSyncSettings).DeterministicEmulation;
+
             switch (SyncSettings.MachineType)
             {
                 case MachineType.ZXSpectrum16:
diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/readme.md b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/readme.md
index 621411f812..6cc05397c2 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/readme.md
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/readme.md
@@ -18,6 +18,7 @@ At the moment this is very experimental and is still actively being worked on.
 * IStatable
 * ISettable core settings
 * IDebuggable (for what it's worth)
+* DeterministicEmulation as a SyncSetting
 * Tape auto-loading routines (as a setting)
 
 ### Work in progress