make fields readonly where possible

src/BizHawk.Client.Common/Sound/Utilities/BufferedAsync.cs

@@ -37,7 +37,7 @@ namespace BizHawk.Client.Common
 		private readonly Queue<short> buffer = new Queue<short>(MaxExcessSamples);
 
 		private int SamplesInOneFrame = 1470;
-		private int TargetExtraSamples = 882;
+		private readonly int TargetExtraSamples = 882;
 		private const int MaxExcessSamples = 4096;
 
 		/// <summary>

src/BizHawk.Client.Common/controllers/AutofireController.cs

@@ -22,7 +22,7 @@ namespace BizHawk.Client.Common
 		private readonly WorkingDictionary<string, bool> _buttons = new WorkingDictionary<string, bool>();
 		private readonly WorkingDictionary<string, int> _buttonStarts = new WorkingDictionary<string, int>();
 
-		private bool _autofire = true;
+		private readonly bool _autofire = true;
 
 		public int On { get; set; }
 		public int Off { get; set; }

src/BizHawk.Common/DeepEquality.cs

@@ -49,7 +49,7 @@ namespace BizHawk.Common
 			}
 		}
 
-		private static MethodInfo ArrayEqualsGeneric = typeof(DeepEquality).GetMethod("ArrayEquals", BindingFlags.NonPublic | BindingFlags.Static);
+		private static readonly MethodInfo ArrayEqualsGeneric = typeof(DeepEquality).GetMethod("ArrayEquals", BindingFlags.NonPublic | BindingFlags.Static);
 
 		/// <summary>test if two objects <paramref name="o1"/> and <paramref name="o2"/> are equal, field-by-field (with deep inspection of each field)</summary>
 		/// <exception cref="InvalidOperationException"><paramref name="o1"/> is an array with rank > 1 or is a non-zero-indexed array</exception>

src/BizHawk.Common/Log.cs

@@ -63,7 +63,7 @@ namespace BizHawk.Common
 		public static Stream HACK_LOG_STREAM;
 
 		private static readonly bool LogToConsole = false;
-		private static bool LogToFile = false;
+		private static readonly bool LogToFile = false;
 
 		private const string LogFilename = "bizhawk.txt";
 		private static StreamWriter writer;

src/BizHawk.Emulation.Common/Database/Database.cs

@@ -13,12 +13,12 @@ namespace BizHawk.Emulation.Common
 {
 	public static class Database
 	{
-		private static Dictionary<string, CompactGameInfo> DB = new Dictionary<string, CompactGameInfo>();
+		private static readonly Dictionary<string, CompactGameInfo> DB = new Dictionary<string, CompactGameInfo>();
 
 		/// <summary>
 		/// blocks until the DB is done loading
 		/// </summary>
-		private static EventWaitHandle acquire = new EventWaitHandle(false, EventResetMode.ManualReset);
+		private static readonly EventWaitHandle acquire = new EventWaitHandle(false, EventResetMode.ManualReset);
 
 		private static string RemoveHashType(string hash)
 		{

src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.cs

@@ -163,12 +163,12 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 		public IInputCallbackSystem InputCallbacks => throw new NotImplementedException();
 
 		private SyncSettings _syncSettings;
-		private Thread _mameThread;
+		private readonly Thread _mameThread;
-		private ManualResetEvent _mameStartupComplete = new ManualResetEvent(false);
+		private readonly ManualResetEvent _mameStartupComplete = new ManualResetEvent(false);
-		private ManualResetEvent _mameFrameComplete = new ManualResetEvent(false);
+		private readonly ManualResetEvent _mameFrameComplete = new ManualResetEvent(false);
-		private ManualResetEvent _memoryAccessComplete = new ManualResetEvent(false);
+		private readonly ManualResetEvent _memoryAccessComplete = new ManualResetEvent(false);
-		private AutoResetEvent _mamePeriodicComplete = new AutoResetEvent(false);
+		private readonly AutoResetEvent _mamePeriodicComplete = new AutoResetEvent(false);
-		private SortedDictionary<string, string> _fieldsPorts = new SortedDictionary<string, string>();
+		private readonly SortedDictionary<string, string> _fieldsPorts = new SortedDictionary<string, string>();
 		private SortedDictionary<string, string> _romHashes = new SortedDictionary<string, string>();
 		private IController _controller = NullController.Instance;
 		private IMemoryDomains _memoryDomains;
@@ -177,15 +177,15 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 		private int _systemBusAddressShift = 0;
 		private bool _memAccess = false;
 		private int[] _frameBuffer = new int[0];
-		private Queue<short> _audioSamples = new Queue<short>();
+		private readonly Queue<short> _audioSamples = new Queue<short>();
 		private decimal _dAudioSamples = 0;
-		private int _sampleRate = 44100;
+		private readonly int _sampleRate = 44100;
 		private int _numSamples = 0;
 		private bool _paused = true;
 		private bool _exiting = false;
 		private bool _frameDone = true;
-		private string _gameDirectory;
+		private readonly string _gameDirectory;
-		private string _gameFilename;
+		private readonly string _gameFilename;
 		private string _gameName = "Arcade";
 		private string _loadFailure = "";
 		private LibMAME.PeriodicCallbackDelegate _periodicCallback;

src/BizHawk.Emulation.Cores/CPUs/CP1610/CP1610.cs

@@ -60,7 +60,7 @@ namespace BizHawk.Emulation.Cores.Components.CP1610
 		public Func<ushort, bool, ushort> ReadMemory;
 		public Func<ushort, ushort, bool, bool> WriteMemory;
 
-		private static bool Logging = false;
+		private static readonly bool Logging = false;
 		private static readonly StreamWriter Log;
 
 		public void SyncState(Serializer ser)

src/BizHawk.Emulation.Cores/CPUs/Intel8048/Disassembler.cs

@@ -6,7 +6,7 @@ namespace BizHawk.Emulation.Cores.Components.I8048
 {
 	public sealed partial class I8048
 	{
-		static string[] table =
+		static readonly string[] table =
 		{
 			"NOP", // 00
 			"???", // 01

src/BizHawk.Emulation.Cores/CPUs/LR35902/Interrupts.cs

@@ -56,7 +56,7 @@ namespace BizHawk.Emulation.Cores.Components.LR35902
 						OP };
 		}
 
-		private static ushort[] INT_vectors = { 0x40, 0x48, 0x50, 0x58, 0x60, 0x00 };
+		private static readonly ushort[] INT_vectors = { 0x40, 0x48, 0x50, 0x58, 0x60, 0x00 };
 
 		public ushort int_src;
 		public byte int_clear;

src/BizHawk.Emulation.Cores/CPUs/LR35902/NewDisassembler.cs

@@ -7,7 +7,7 @@ namespace BizHawk.Emulation.Cores.Components.LR35902
 	// adapted from the information at http://www.pastraiser.com/cpu/gameboy/gameboy_opcodes.html
 	public sealed partial class LR35902
 	{
-		static string[] table =
+		static readonly string[] table =
 		{
 			"NOP", // 00
 			"LD   BC,d16", // 01

src/BizHawk.Emulation.Cores/CPUs/MC6800/Disassembler.cs

@@ -6,7 +6,7 @@ namespace BizHawk.Emulation.Cores.Components.MC6800
 {
 	public sealed partial class MC6800
 	{
-		static string[] table =
+		static readonly string[] table =
 		{
 			"???", // 00
 			"NOP", // 01

src/BizHawk.Emulation.Cores/CPUs/MC6809/Disassembler.cs

@@ -6,7 +6,7 @@ namespace BizHawk.Emulation.Cores.Components.MC6809
 {
 	public sealed partial class MC6809
 	{
-		static string[] table =
+		static readonly string[] table =
 		{
 			"NEG   DP+i8", // 00
 			"???", // 01
@@ -266,7 +266,7 @@ namespace BizHawk.Emulation.Cores.Components.MC6809
 			"ST    U,ex16", // ff
 		};
 
-		static string[] table2 =
+		static readonly string[] table2 =
 		{
 			"???", // 00
 			"???", // 01
@@ -526,7 +526,7 @@ namespace BizHawk.Emulation.Cores.Components.MC6809
 			"ST    SP,ex16", // ff
 		};
 
-		static string[] table3 =
+		static readonly string[] table3 =
 		{
 			"???", // 00
 			"???", // 01

src/BizHawk.Emulation.Cores/CPUs/MOS 6502X/Execute.cs

@@ -30,7 +30,7 @@ namespace BizHawk.Emulation.Cores.Components.M6502
 			//    CompiledMicrocode[i] = (short)temp[i];
 		}
 
-		static Uop[][] Microcode =
+		static readonly Uop[][] Microcode =
 		{
 			//0x00
 			/*BRK [implied]*/ new Uop[] { Uop.Fetch2, Uop.PushPCH, Uop.PushPCL, Uop.PushP_BRK, Uop.FetchPCLVector, Uop.FetchPCHVector, Uop.End_SuppressInterrupt },

src/BizHawk.Emulation.Cores/CPUs/W65816/Disassembler.cs

@@ -21,7 +21,7 @@ namespace BizHawk.Emulation.Cores.Components.W65816
 	{
 		public string Cpu { get; set; }
 
-		W65816 disassemblerCpu = new W65816();
+		readonly W65816 disassemblerCpu = new W65816();
 		
 		public IEnumerable<string> AvailableCpus
 		{

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/AmstradCPC.ISettable.cs

@@ -158,7 +158,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 			public string Media { get; set; }
 			public string OtherMisc { get; set; }
 
-			Dictionary<string, string> Data = new Dictionary<string, string>();
+			readonly Dictionary<string, string> Data = new Dictionary<string, string>();
 
 			public static CPCMachineMetaData GetMetaObject(MachineType type)
 			{

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/Disk/NECUPD765.FDD.cs

@@ -43,7 +43,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// Array that holds state information for each possible drive
 		/// </summary>
-		private DriveState[] DriveStates = new DriveState[4];
+		private readonly DriveState[] DriveStates = new DriveState[4];
 
 		/// <summary>
 		/// Initialization / reset of the floppy drive subsystem
@@ -283,7 +283,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 			/// <summary>
 			/// The parent controller
 			/// </summary>
-			private NECUPD765 FDC;
+			private readonly NECUPD765 FDC;
 
 			/// <summary>
 			/// TRUE if we are on track 0

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/Disk/NECUPD765.IPortIODevice.cs

@@ -36,7 +36,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
          * MK flag
          * SK flag
          * */
-		private string[] workingArr = new string[3];
+		private readonly string[] workingArr = new string[3];
 
 		private void BuildCSVLine()
 		{

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/Display/AmstradGateArray.cs

@@ -16,7 +16,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 	/// </summary>
 	public class AmstradGateArray : IPortIODevice, IVideoProvider
 	{
-		private CPCBase _machine;
+		private readonly CPCBase _machine;
 		private Z80A CPU => _machine.CPU;
 		private CRCT_6845 CRCT => _machine.CRCT;
 		//private CRTDevice CRT => _machine.CRT;
@@ -679,18 +679,18 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// The current character line we are working from
 		/// </summary>
-		private CharacterLine CurrentLine;
+		private readonly CharacterLine CurrentLine;
 
 		/// <summary>
 		/// List of screen lines as they are built up
 		/// </summary>
-		private List<CharacterLine> ScreenLines = new List<CharacterLine>();
+		private readonly List<CharacterLine> ScreenLines = new List<CharacterLine>();
 
 		/// <summary>
 		/// Pixel value lookups for every scanline byte value
 		/// Based on the lookup at https://github.com/gavinpugh/xnacpc
 		/// </summary>
-		private int[][] ByteLookup = new int[4][];
+		private readonly int[][] ByteLookup = new int[4][];
 		private void InitByteLookup()
 		{
 			int pix;

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/Display/CRCT_6845.cs

@@ -364,14 +364,14 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// http://www.cantrell.org.uk/david/tech/cpc/cpc-firmware/firmware.pdf
 		/// (The defaults values given here are those programmed by the firmware ROM after a cold/warm boot of the CPC/Plus)
 		/// </summary>
-		private byte[] RegDefaults = { 63, 40, 46, 112, 38, 0, 25, 30, 0, 7, 0, 0, 48, 0, 192, 7, 0, 0 };
+		private readonly byte[] RegDefaults = { 63, 40, 46, 112, 38, 0, 25, 30, 0, 7, 0, 0, 48, 0, 192, 7, 0, 0 };
 
 		/// <summary>
 		/// Register masks
 		/// 0 = WRITE
 		/// 1 = READ
 		/// </summary>
-		private byte[] CPCMask = { 255, 255, 255, 255, 127, 31, 127, 126, 3, 31, 31, 31, 63, 255, 63, 255, 63, 255 };
+		private readonly byte[] CPCMask = { 255, 255, 255, 255, 127, 31, 127, 126, 3, 31, 31, 31, 63, 255, 63, 255, 63, 255 };
 
 		/// <summary>
 		/// Horizontal Character Count

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/Display/CRTDevice.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 	/// </summary>
 	public class CRTDevice : IVideoProvider
 	{
-		private CPCBase _machine;
+		private readonly CPCBase _machine;
 		private CRCT_6845 CRCT => _machine.CRCT;
 		private AmstradGateArray GateArray => _machine.GateArray;
 
@@ -250,7 +250,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// The calling CRT device
 		/// </summary>
-		private CRTDevice CRT;
+		private readonly CRTDevice CRT;
 
 		public ScanLine(CRTDevice crt)
 		{

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/PPI/PPI_8255.cs

@@ -11,7 +11,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 	/// </summary>
 	public class PPI_8255 : IPortIODevice
 	{
-		private CPCBase _machine;
+		private readonly CPCBase _machine;
 		private CRCT_6845 CRTC => _machine.CRCT;
 		private AmstradGateArray GateArray => _machine.GateArray;
 		private IPSG PSG => _machine.AYDevice;

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/SoundOutput/AY38912.cs

@@ -16,7 +16,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// The emulated machine (passed in via constructor)
 		/// </summary>
-		private CPCBase _machine;
+		private readonly CPCBase _machine;
 		private IKeyboard _keyboard => _machine.KeyboardDevice;
 
 		private int _tStatesPerFrame;
@@ -409,7 +409,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// The frequency of the AY chip
 		/// </summary>
-		private static int _chipFrequency = 1000000; // 1773400;
+		private static readonly int _chipFrequency = 1000000; // 1773400;
 
 		/// <summary>
 		/// The rendering resolution of the chip
@@ -504,7 +504,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// Panning table list
 		/// </summary>
-		private static List<uint[]> PanTabs = new List<uint[]>
+		private static readonly List<uint[]> PanTabs = new List<uint[]>
 		{
             // MONO
             new uint[] { 50,50, 50,50, 50,50 },
@@ -540,7 +540,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// Volume table to be used
 		/// </summary>
-		private static uint[] AYVolumes =
+		private static readonly uint[] AYVolumes =
 		{
 			0x0000,0x0000,0x0340,0x0340,0x04C0,0x04C0,0x06F2,0x06F2,
 			0x0A44,0x0A44,0x0F13,0x0F13,0x1510,0x1510,0x227E,0x227E,

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/SoundOutput/Beeper.cs

@@ -53,7 +53,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// The parent emulated machine
 		/// </summary>
-		private CPCBase _machine;
+		private readonly CPCBase _machine;
 
 		/// <summary>
 		/// The last pulse

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Machine/CPCBase.Input.cs

@@ -6,23 +6,23 @@
 	/// </summary>
 	public abstract partial class CPCBase
 	{
-		string Play = "Play Tape";
+		readonly string Play = "Play Tape";
-		string Stop = "Stop Tape";
+		readonly string Stop = "Stop Tape";
-		string RTZ = "RTZ Tape";
+		readonly string RTZ = "RTZ Tape";
-		string Record = "Record Tape";
+		readonly string Record = "Record Tape";
-		string NextTape = "Insert Next Tape";
+		readonly string NextTape = "Insert Next Tape";
-		string PrevTape = "Insert Previous Tape";
+		readonly string PrevTape = "Insert Previous Tape";
-		string NextBlock = "Next Tape Block";
+		readonly string NextBlock = "Next Tape Block";
-		string PrevBlock = "Prev Tape Block";
+		readonly string PrevBlock = "Prev Tape Block";
-		string TapeStatus = "Get Tape Status";
+		readonly string TapeStatus = "Get Tape Status";
 
-		string NextDisk = "Insert Next Disk";
+		readonly string NextDisk = "Insert Next Disk";
-		string PrevDisk = "Insert Previous Disk";
+		readonly string PrevDisk = "Insert Previous Disk";
-		string EjectDisk = "Eject Current Disk";
+		readonly string EjectDisk = "Eject Current Disk";
-		string DiskStatus = "Get Disk Status";
+		readonly string DiskStatus = "Get Disk Status";
 
-		string HardResetStr = "Power";
+		readonly string HardResetStr = "Power";
-		string SoftResetStr = "Reset";
+		readonly string SoftResetStr = "Reset";
 
 		bool pressed_Play = false;
 		bool pressed_Stop = false;

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Machine/GateArrayBase.cs

@@ -16,7 +16,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		public int Z80ClockSpeed = 4000000;
 		public int FrameLength = 79872;
 
-		private CPCBase _machine;
+		private readonly CPCBase _machine;
 		private Z80A CPU => _machine.CPU;
 		private CRCT_6845 CRCT => _machine.CRCT;
 		private IPSG PSG => _machine.AYDevice;
@@ -190,13 +190,13 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 			}
 		}
 
-		private int[] PenColours;
+		private readonly int[] PenColours;
 		private int CurrentPen;
 		private int ScreenMode;
 		private int INTScanlineCnt;
 		//private int VSYNCDelyCnt;
 
-		private int[][] Lookup = new int[4][];
+		private readonly int[][] Lookup = new int[4][];
 
 		//private bool DoModeUpdate;
 

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Media/Tape/CDT/CdtConverter.cs

@@ -13,7 +13,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// The type of serializer
 		/// </summary>
-		private MediaConverterType _formatType = MediaConverterType.CDT;
+		private readonly MediaConverterType _formatType = MediaConverterType.CDT;
 		public override MediaConverterType FormatType => _formatType;
 
 		/// <summary>
@@ -39,9 +39,9 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// Object to keep track of loops - this assumes there is only one loop at a time
 		/// </summary>
-		private List<KeyValuePair<int, int>> _loopCounter = new List<KeyValuePair<int, int>>();
+		private readonly List<KeyValuePair<int, int>> _loopCounter = new List<KeyValuePair<int, int>>();
 
-		private DatacorderDevice _datacorder;
+		private readonly DatacorderDevice _datacorder;
 
 		public CdtConverter(DatacorderDevice _tapeDevice)
 		{

src/BizHawk.Emulation.Cores/Computers/AppleII/AppleII.cs

@@ -59,7 +59,7 @@ namespace BizHawk.Emulation.Cores.Computers.AppleII
 		private readonly List<byte[]> _romSet = new List<byte[]>();
 		private readonly ITraceable _tracer;
 
-		private Components _machine;
+		private readonly Components _machine;
 		private byte[] _disk1;
 		private readonly byte[] _appleIIRom;
 		private readonly byte[] _diskIIRom;

src/BizHawk.Emulation.Cores/Computers/AppleII/Components/EmptyPeripheralComponent.cs

@@ -8,7 +8,7 @@ namespace BizHawk.Emulation.Cores.Computers.AppleII
 	public class EmptyPeripheralCard : IPeripheralCard
 	{
 		// TODO: make readonly once json isn't used
-		private Video _video;
+		private readonly Video _video;
 
 		// TODO: remove when json isn't used
 		public EmptyPeripheralCard() { }

src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper0020.cs

@@ -26,8 +26,8 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.Cartridge
 	{
 		private int _bankOffset = 63 << 13;
 
-		private int[] _banksA = new int[64 << 13]; // 8000
+		private readonly int[] _banksA = new int[64 << 13]; // 8000
-		private int[] _banksB = new int[64 << 13]; // A000
+		private readonly int[] _banksB = new int[64 << 13]; // A000
 
 		private readonly int[] _originalMediaA; // 8000
 		private readonly int[] _originalMediaB; // A000

src/BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Vic.Sprite.cs

@@ -12,7 +12,7 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
 			public bool Display;
 			public bool Dma;
 			public bool Enable;
-			public int Index;
+			public readonly int Index;
 			public int Loaded;
 			public int Mc;
 			public int Mcbase;

src/BizHawk.Emulation.Cores/Computers/MSX/MSX.cs

@@ -114,20 +114,20 @@ namespace BizHawk.Emulation.Cores.Computers.MSX
 		// Machine resources
 		private IController _controller = NullController.Instance;
 
-		private ControllerDefinition current_controller = null;
+		private readonly ControllerDefinition current_controller = null;
 
 		private int _frame = 0;
 
 		public DisplayType Region => DisplayType.NTSC;
 
-		private ITraceable Tracer;
+		private readonly ITraceable Tracer;
 
 		private LibMSX.TraceCallback tracecb;
 
 		// these will be constant values assigned during core construction
 		private int Header_Length;
-		private int Disasm_Length;
+		private readonly int Disasm_Length;
-		private int Reg_String_Length;
+		private readonly int Reg_String_Length;
 
 		private void MakeTrace(int t)
 		{
@@ -144,7 +144,7 @@ namespace BizHawk.Emulation.Cores.Computers.MSX
 			});
 		}
 
-		private MemoryCallbackSystem _memorycallbacks = new MemoryCallbackSystem(new[] { "System Bus" });
+		private readonly MemoryCallbackSystem _memorycallbacks = new MemoryCallbackSystem(new[] { "System Bus" });
 		public IMemoryCallbackSystem MemoryCallbacks => _memorycallbacks;
 	}
 }

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/Disk/NECUPD765.FDD.cs

@@ -43,7 +43,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// Array that holds state information for each possible drive
 		/// </summary>
-		private DriveState[] DriveStates = new DriveState[4];
+		private readonly DriveState[] DriveStates = new DriveState[4];
 
 		/// <summary>
 		/// Initialization / reset of the floppy drive subsystem
@@ -283,7 +283,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			/// <summary>
 			/// The parent controller
 			/// </summary>
-			private NECUPD765 FDC;
+			private readonly NECUPD765 FDC;
 
 			/// <summary>
 			/// TRUE if we are on track 0

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/Disk/NECUPD765.IPortIODevice.cs

@@ -36,7 +36,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
          * MK flag
          * SK flag
          * */
-        private string[] workingArr = new string[3];
+        private readonly string[] workingArr = new string[3];
 
         private void BuildCSVLine()
         {

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/Input/CursorJoystick.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	public class CursorJoystick : IJoystick
 	{
 		//private int _joyLine;
-		private SpectrumBase _machine;
+		private readonly SpectrumBase _machine;
 
 		public CursorJoystick(SpectrumBase machine, int playerNumber)
 		{
@@ -28,7 +28,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			}.ToArray();
 		}
 
-		private List<string> btnLookups = new List<string>
+		private readonly List<string> btnLookups = new List<string>
 		{
 			"Key 5",    // left
             "Key 8",    // right

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/Input/SinclairJoystick1.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	public class SinclairJoystick1 : IJoystick
 	{
 		//private int _joyLine;
-		private SpectrumBase _machine;
+		private readonly SpectrumBase _machine;
 
 		public SinclairJoystick1(SpectrumBase machine, int playerNumber)
 		{
@@ -28,7 +28,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			}.ToArray();
 		}
 
-		private List<string> btnLookups = new List<string>
+		private readonly List<string> btnLookups = new List<string>
 		{
 			"Key 1",    // left
             "Key 2",    // right

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/Input/SinclairJoystick2.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	public class SinclairJoystick2 : IJoystick
 	{
 		//private int _joyLine;
-		private SpectrumBase _machine;
+		private readonly SpectrumBase _machine;
 
 		public SinclairJoystick2(SpectrumBase machine, int playerNumber)
 		{
@@ -28,7 +28,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			}.ToArray();
 		}
 
-		private List<string> btnLookups = new List<string>
+		private readonly List<string> btnLookups = new List<string>
 		{
 			"Key 6",    // left
             "Key 7",    // right

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/SoundOuput/AY38912.cs

@@ -20,7 +20,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// The emulated machine (passed in via constructor)
 		/// </summary>
-		private SpectrumBase _machine;
+		private readonly SpectrumBase _machine;
 
 		private int _tStatesPerFrame;
 		private int _sampleRate;
@@ -401,7 +401,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// The frequency of the AY chip
 		/// </summary>
-		private static int _chipFrequency = 1773400;
+		private static readonly int _chipFrequency = 1773400;
 
 		/// <summary>
 		/// The rendering resolution of the chip
@@ -496,7 +496,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// Panning table list
 		/// </summary>
-		private static List<uint[]> PanTabs = new List<uint[]>
+		private static readonly List<uint[]> PanTabs = new List<uint[]>
 		{
             // MONO
             new uint[] { 50,50, 50,50, 50,50 },
@@ -532,7 +532,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// Volume table to be used
 		/// </summary>
-		private static uint[] AYVolumes =
+		private static readonly uint[] AYVolumes =
 		{
 			0x0000,0x0000,0x0340,0x0340,0x04C0,0x04C0,0x06F2,0x06F2,
 			0x0A44,0x0A44,0x0F13,0x0F13,0x1510,0x1510,0x227E,0x227E,

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/CPUMonitor.cs

@@ -9,8 +9,8 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// </summary>
 	public class CPUMonitor
 	{
-		private SpectrumBase _machine;
+		private readonly SpectrumBase _machine;
-		private Z80A _cpu;
+		private readonly Z80A _cpu;
 		public MachineType machineType = MachineType.ZXSpectrum48;
 
 		/// <summary>

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/SpectrumBase.Input.cs

@@ -9,23 +9,23 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// </summary>
 	public abstract partial class SpectrumBase
 	{
-		string Play = "Play Tape";
+		readonly string Play = "Play Tape";
-		string Stop = "Stop Tape";
+		readonly string Stop = "Stop Tape";
-		string RTZ = "RTZ Tape";
+		readonly string RTZ = "RTZ Tape";
-		string Record = "Record Tape";
+		readonly string Record = "Record Tape";
-		string NextTape = "Insert Next Tape";
+		readonly string NextTape = "Insert Next Tape";
-		string PrevTape = "Insert Previous Tape";
+		readonly string PrevTape = "Insert Previous Tape";
-		string NextBlock = "Next Tape Block";
+		readonly string NextBlock = "Next Tape Block";
-		string PrevBlock = "Prev Tape Block";
+		readonly string PrevBlock = "Prev Tape Block";
-		string TapeStatus = "Get Tape Status";
+		readonly string TapeStatus = "Get Tape Status";
 
-		string NextDisk = "Insert Next Disk";
+		readonly string NextDisk = "Insert Next Disk";
-		string PrevDisk = "Insert Previous Disk";
+		readonly string PrevDisk = "Insert Previous Disk";
-		string EjectDisk = "Eject Current Disk";
+		readonly string EjectDisk = "Eject Current Disk";
-		string DiskStatus = "Get Disk Status";
+		readonly string DiskStatus = "Get Disk Status";
 
-		string HardResetStr = "Power";
+		readonly string HardResetStr = "Power";
-		string SoftResetStr = "Reset";
+		readonly string SoftResetStr = "Reset";
 
 		bool pressed_Play;
 		bool pressed_Stop;

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULA.cs

@@ -253,7 +253,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			/// <summary>
 			/// The ULA device
 			/// </summary>
-			private ULA _ula;
+			private readonly ULA _ula;
 
 			/// <summary>
 			/// Array of rendercycle entries

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Snapshot/SZX/SZX.Methods.cs

@@ -12,7 +12,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// </summary>
 	public partial class SZX
 	{
-		private SpectrumBase _machine;
+		private readonly SpectrumBase _machine;
 
 		private Z80A _cpu => _machine.CPU;
 

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/CSW/CswConverter.cs

@@ -14,7 +14,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// The type of serializer
 		/// </summary>
-		private MediaConverterType _formatType = MediaConverterType.CSW;
+		private readonly MediaConverterType _formatType = MediaConverterType.CSW;
 		public override MediaConverterType FormatType => _formatType;
 
 		/// <summary>
@@ -32,7 +32,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public override bool IsWriter => false;
 
-		private DatacorderDevice _datacorder;
+		private readonly DatacorderDevice _datacorder;
 
 		public CswConverter(DatacorderDevice _tapeDevice)
 		{

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/PZX/PzxConverter.cs

@@ -14,7 +14,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// The type of serializer
 		/// </summary>
-		private MediaConverterType _formatType = MediaConverterType.PZX;
+		private readonly MediaConverterType _formatType = MediaConverterType.PZX;
 		public override MediaConverterType FormatType => _formatType;
 
 		/// <summary>
@@ -42,7 +42,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		private List<KeyValuePair<int, int>> _loopCounter = new List<KeyValuePair<int, int>>();
 
-		private DatacorderDevice _datacorder;
+		private readonly DatacorderDevice _datacorder;
 
 		public PzxConverter(DatacorderDevice _tapeDevice)
 		{

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/TAP/TapConverter.cs

@@ -14,7 +14,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// The type of serializer
 		/// </summary>
-		private MediaConverterType _formatType = MediaConverterType.TAP;
+		private readonly MediaConverterType _formatType = MediaConverterType.TAP;
 		public override MediaConverterType FormatType => _formatType;
 
 		/// <summary>
@@ -27,7 +27,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public override bool IsWriter => false;
 
-		private DatacorderDevice _datacorder;
+		private readonly DatacorderDevice _datacorder;
 
 		public TapConverter(DatacorderDevice _tapeDevice)
 		{

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/TZX/TzxConverter.cs

@@ -13,7 +13,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// The type of serializer
 		/// </summary>
-		private MediaConverterType _formatType = MediaConverterType.TZX;
+		private readonly MediaConverterType _formatType = MediaConverterType.TZX;
 		public override MediaConverterType FormatType => _formatType;
 
 		/// <summary>
@@ -39,9 +39,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// Object to keep track of loops - this assumes there is only one loop at a time
 		/// </summary>
-		private List<KeyValuePair<int, int>> _loopCounter = new List<KeyValuePair<int, int>>();
+		private readonly List<KeyValuePair<int, int>> _loopCounter = new List<KeyValuePair<int, int>>();
 
-		private DatacorderDevice _datacorder;
+		private readonly DatacorderDevice _datacorder;
 
 		public TzxConverter(DatacorderDevice _tapeDevice)
 		{

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/WAV/WavConverter.cs

@@ -14,7 +14,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// The type of serializer
 		/// </summary>
-		private MediaConverterType _formatType = MediaConverterType.WAV;
+		private readonly MediaConverterType _formatType = MediaConverterType.WAV;
 		public override MediaConverterType FormatType => _formatType;
 
 		/// <summary>
@@ -31,7 +31,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// Position counter
 		/// </summary>
 		//private int _position = 0;
-		private DatacorderDevice _datacorder;
+		private readonly DatacorderDevice _datacorder;
 
 		public WavConverter(DatacorderDevice _tapeDevice)
 		{

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/WAV/WavStreamReader.cs

@@ -8,8 +8,8 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// </summary>
 	public class WavStreamReader
 	{
-		private Stream m_stream;
+		private readonly Stream m_stream;
-		private WavHeader m_header = new WavHeader();
+		private readonly WavHeader m_header = new WavHeader();
 
 		public WavStreamReader(Stream stream)
 		{

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.ISettable.cs

@@ -234,7 +234,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		public string Media { get; set; }
 		public string OtherMisc { get; set; }
 
-		private Dictionary<string, string> Data = new Dictionary<string, string>();
+		private readonly Dictionary<string, string> Data = new Dictionary<string, string>();
 
 		/// <summary>
 		/// Detailed info to be displayed within the settings UIs

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.cs

@@ -168,12 +168,12 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 
 		public bool DiagRom = false;
 
-		private List<string> diagRoms = new List<string>
+		private readonly List<string> diagRoms = new List<string>
 		{
 			@"\DiagROM.v28",
 			@"\zx-diagnostics\testrom.bin"
 		};
-		private int diagIndex = 1;
+		private readonly int diagIndex = 1;
 
 		internal CoreComm CoreComm { get; }
 

src/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs

@@ -58,7 +58,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 
 		public int NominalNumScanlines => _pal ? 312 : 262;
 
-		private int[] _scanlinebuffer = new int[ScreenWidth * MaxScreenHeight];
+		private readonly int[] _scanlinebuffer = new int[ScreenWidth * MaxScreenHeight];
 
 		private int[] _palette;
 

src/BizHawk.Emulation.Cores/Consoles/Atari/A7800Hawk/Maria.cs

@@ -24,7 +24,7 @@ namespace BizHawk.Emulation.Cores.Atari.A7800Hawk
 
 		// technically there is no limit on the number of graphics objects, but since dma is automatically killed
 		// at the end of a scanline, we have an effective limit
-		GFX_Object[] GFX_Objects = new GFX_Object[128];
+		readonly GFX_Object[] GFX_Objects = new GFX_Object[128];
 
 		public byte[,] line_ram = new byte[2, 320];
 		byte temp_check = 0;

src/BizHawk.Emulation.Cores/Consoles/Belogic/Uzem.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Belogic
 	public class Uzem : WaterboxCore
 	{
 		private LibUzem _uze;
-		private bool _mouseEnabled;
+		private readonly bool _mouseEnabled;
 
 		[CoreConstructor("UZE")]
 		public Uzem(CoreComm comm, byte[] rom)

src/BizHawk.Emulation.Cores/Consoles/Fairchild/ChannelF/Audio.cs

@@ -8,7 +8,7 @@ namespace BizHawk.Emulation.Cores.Consoles.ChannelF
 	/// </summary>
 	public partial class ChannelF : ISoundProvider
 	{
-		private double SampleRate = 44100;
+		private readonly double SampleRate = 44100;
 		private int SamplesPerFrame;
 		private double Period;
 		private double CyclesPerSample;
@@ -16,7 +16,7 @@ namespace BizHawk.Emulation.Cores.Consoles.ChannelF
 
 		private int tone = 0;
 
-		private double[] tone_freqs = { 0, 1000, 500, 120 };
+		private readonly double[] tone_freqs = { 0, 1000, 500, 120 };
 #pragma warning disable CS0414
 		private double amplitude = 0;
 		private double decay = 0.998;

src/BizHawk.Emulation.Cores/Consoles/Fairchild/ChannelF/ChannelF.IEmulator.cs

@@ -12,8 +12,8 @@ namespace BizHawk.Emulation.Cores.Consoles.ChannelF
 
 		public bool DeterministicEmulation { get; set; }
 
-		private static double cpuFreq = 1.7897725;
+		private static readonly double cpuFreq = 1.7897725;
-		private static double refreshRate = 60;
+		private static readonly double refreshRate = 60;
 
 		public int ClockPerFrame;
 		public int FrameClock = 0;

src/BizHawk.Emulation.Cores/Consoles/Fairchild/ChannelF/Video.cs

@@ -43,7 +43,7 @@ namespace BizHawk.Emulation.Cores.Consoles.ChannelF
 		private int _y;
 		private int _arm;
 
-		private int[] frameBuffer = new int[128 * 64];
+		private readonly int[] frameBuffer = new int[128 * 64];
 
 		private void BuildFrame()
 		{

src/BizHawk.Emulation.Cores/Consoles/Intellivision/Controllers/IntellivisionControllers.cs

@@ -96,7 +96,7 @@ namespace BizHawk.Emulation.Cores.Intellivision
 			"S", "SSW", "SW", "WSW", "W", "WNW", "NW", "NNW",
 		};
 
-		private static byte[] HandControllerButtons =
+		private static readonly byte[] HandControllerButtons =
 		{
 			0x60, // OUTPUT_ACTION_BUTTON_BOTTOM_LEFT
 			0xC0, // OUTPUT_ACTION_BUTTON_BOTTOM_RIGHT
@@ -177,7 +177,7 @@ namespace BizHawk.Emulation.Cores.Intellivision
 			"Key 6", "Key 7", "Key 8", "Key 9", "Enter", "Clear"
 		};
 
-		private static byte[] BoolControllerButtons =
+		private static readonly byte[] BoolControllerButtons =
 		{
 			0x60, // OUTPUT_ACTION_BUTTON_BOTTOM_LEFT
 			0xC0, // OUTPUT_ACTION_BUTTON_BOTTOM_RIGHT
@@ -217,7 +217,7 @@ namespace BizHawk.Emulation.Cores.Intellivision
 
 		private const int Deadzone = 50;
 
-		private static byte[] FloatControllerButtons =
+		private static readonly byte[] FloatControllerButtons =
 		{
 			0x02, // E
 			0x06, // ENE

src/BizHawk.Emulation.Cores/Consoles/Intellivision/STIC.cs

@@ -22,7 +22,7 @@ namespace BizHawk.Emulation.Cores.Intellivision
 		public Func<ushort, bool, ushort> ReadMemory;
 		public Func<ushort, ushort, bool, bool> WriteMemory;
 
-		private static int BORDER_OFFSET=176*8;
+		private static readonly int BORDER_OFFSET=176*8;
 
 		public int[] BGBuffer = new int[159 * 96];
 		public int[] FrameBuffer = new int[176 * 208];

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBHawk.cs

@@ -76,7 +76,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 		public byte undoc_6C, undoc_72, undoc_73, undoc_74, undoc_75, undoc_76, undoc_77;
 
 		public byte[] _bios;
-		public readonly byte[] _rom;		
+		public readonly byte[] _rom;
 		public readonly byte[] header = new byte[0x50];
 
 		public byte[] cart_RAM;
@@ -98,7 +98,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 		public Audio audio;
 		public SerialPort serialport;
 
-		private static byte[] GBA_override = { 0xFF, 0x00, 0xCD, 0x03, 0x35, 0xAA, 0x31, 0x90, 0x94, 0x00, 0x00, 0x00, 0x00 };
+		private static readonly byte[] GBA_override = { 0xFF, 0x00, 0xCD, 0x03, 0x35, 0xAA, 0x31, 0x90, 0x94, 0x00, 0x00, 0x00, 0x00 };
 
 		[CoreConstructor("GB")]
 		[CoreConstructor("GBC")]

src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/GambatteLink.IInputPollable.cs

@@ -10,6 +10,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 
 		public IInputCallbackSystem InputCallbacks => _inputCallbacks;
 
-		private InputCallbackSystem _inputCallbacks = new InputCallbackSystem();
+		private readonly InputCallbackSystem _inputCallbacks = new InputCallbackSystem();
 	}
 }

src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/GambatteLink.IStatable.cs

@@ -74,7 +74,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 			_cablediscosignal = reader.ReadBoolean();
 		}
 
-		private JsonSerializer ser = new JsonSerializer { Formatting = Formatting.Indented };
+		private readonly JsonSerializer ser = new JsonSerializer { Formatting = Formatting.Indented };
 
 		private class DGBSerialized
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/GambattePrinter.cs

@@ -38,8 +38,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 
 		const ushort SerialIRQAddress = 0x58;
 
-		Gameboy gb;
+		readonly Gameboy gb;
-		PrinterCallback callback;
+		readonly PrinterCallback callback;
 		LibGambatte.LinkCallback linkCallback;
 
 		CommandState command_state;
@@ -47,12 +47,12 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 
 		bool compression;
 		ushort length_left;
-		byte[] command_data = new byte[GB_PRINTER_MAX_COMMAND_LENGTH];
+		readonly byte[] command_data = new byte[GB_PRINTER_MAX_COMMAND_LENGTH];
 		ushort command_length;
 		ushort checksum;
 		byte status;
 
-		byte[] image = new byte[160 * 200];
+		readonly byte[] image = new byte[160 * 200];
 		ushort image_offset;
 
 		byte compression_run_lenth;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/Sameboy.cs

@@ -31,9 +31,9 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.Gameboy
 		/// </summary>
 		private const int TICKSPERSECOND_SGB = 2147727;
 
-		private LibSameboy _core;
+		private readonly LibSameboy _core;
-		private bool _cgb;
+		private readonly bool _cgb;
-		private bool _sgb;
+		private readonly bool _sgb;
 
 		[CoreConstructor("SGB")]
 		public Sameboy(byte[] rom, CoreComm comm, Settings settings, SyncSettings syncSettings, bool deterministic)
@@ -304,7 +304,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.Gameboy
 
 		public bool IsCGBMode() => _cgb;
 
-		private GPUMemoryAreas _gpuMemory;
+		private readonly GPUMemoryAreas _gpuMemory;
 
 		public GPUMemoryAreas GetGPU() => _gpuMemory;
 		private ScanlineCallback _scanlineCallback;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/N64.IMemoryDomains.cs

@@ -9,7 +9,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64
 {
 	public partial class N64
 	{
-		private List<MemoryDomain> _memoryDomains = new List<MemoryDomain>();
+		private readonly List<MemoryDomain> _memoryDomains = new List<MemoryDomain>();
 
 		private IMemoryDomains MemoryDomains;
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/N64.IStatable.cs

@@ -51,6 +51,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64
 			Frame = reader.ReadInt32();
 		}
 
-		private byte[] SaveStatePrivateBuff = new byte[16788288 + 1024];
+		private readonly byte[] SaveStatePrivateBuff = new byte[16788288 + 1024];
 	}
 }

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/N64.cs

@@ -154,11 +154,11 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64
 
 		private bool _pendingThreadTerminate;
 
-		private DisplayType _display_type = DisplayType.NTSC;
+		private readonly DisplayType _display_type = DisplayType.NTSC;
 
 		private Action _pendingThreadAction;
 
-		private bool _disableExpansionSlot = true;
+		private readonly bool _disableExpansionSlot = true;
 
 		public IEmulatorServiceProvider ServiceProvider { get; }
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/N64Audio.cs

@@ -11,7 +11,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64
 		/// </summary>
 		private mupen64plusAudioApi api;
 
-		private mupen64plusApi coreAPI;
+		private readonly mupen64plusApi coreAPI;
 
 		/// <summary>
 		/// Buffer for audio data

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/N64VideoProvider.cs

@@ -8,7 +8,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64
 	{
 		private int[] frameBuffer;
 		private mupen64plusVideoApi api;
-		private mupen64plusApi coreAPI;
+		private readonly mupen64plusApi coreAPI;
 
 		public bool IsVIFrame;
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/NativeApi/mupen64plusAudioApi.cs

@@ -16,7 +16,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 		/// <returns>The size of the mupen64plus audio buffer</returns>
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		private delegate int GetBufferSize();
-		GetBufferSize dllGetBufferSize;
+		readonly GetBufferSize dllGetBufferSize;
 
 		/// <summary>
 		/// Gets the audio buffer from mupen64plus, and then clears it
@@ -24,7 +24,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 		/// <param name="dest">The buffer to fill with samples</param>
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		private delegate void ReadAudioBuffer(short[] dest);
-		ReadAudioBuffer dllReadAudioBuffer;
+		readonly ReadAudioBuffer dllReadAudioBuffer;
 
 		/// <summary>
 		/// Gets the current audio rate from mupen64plus
@@ -32,7 +32,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 		/// <returns>The current audio rate</returns>
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		private delegate int GetAudioRate();
-		GetAudioRate dllGetAudioRate;
+		readonly GetAudioRate dllGetAudioRate;
 
 		/// <summary>
 		/// Loads native functions and attaches itself to the core

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/NativeApi/mupen64plusCoreApi.cs

@@ -19,11 +19,11 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 
 		bool disposed = false;
 
-		Thread m64pEmulator;
+		readonly Thread m64pEmulator;
 
-		AutoResetEvent m64pEvent = new AutoResetEvent(false);
+		readonly AutoResetEvent m64pEvent = new AutoResetEvent(false);
 		AutoResetEvent m64pContinueEvent = new AutoResetEvent(false);
-		ManualResetEvent m64pStartupComplete = new ManualResetEvent(false);
+		readonly ManualResetEvent m64pStartupComplete = new ManualResetEvent(false);
 
 		bool event_frameend = false;
 		bool event_breakpoint = false;
@@ -978,7 +978,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 			public DynamicLibraryImportResolver dllThinWrapper;
 			public PluginShutdown dllShutdown;
 		}
-		Dictionary<m64p_plugin_type, AttachedPlugin> plugins = new Dictionary<m64p_plugin_type, AttachedPlugin>();
+
+		readonly Dictionary<m64p_plugin_type, AttachedPlugin> plugins = new Dictionary<m64p_plugin_type, AttachedPlugin>();
 
 		public IntPtr AttachPlugin(m64p_plugin_type type, string PluginName)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/NativeApi/mupen64plusInputApi.cs

@@ -13,7 +13,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 		/// <param name="inputCallback">The delegate to use</param>
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		private delegate void SetInputCallback(InputCallback inputCallback);
-		SetInputCallback InpSetInputCallback;
+		readonly SetInputCallback InpSetInputCallback;
 
 		/// <summary>
 		/// Callback to use when mupen64plus wants input
@@ -41,7 +41,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 		/// <param name="type">Type id according to (well documented... hurr hurr) mupen api</param>
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		public delegate void SetControllerPakType(int controller, int type);
-		SetControllerPakType InpSetControllerPakType;
+		readonly SetControllerPakType InpSetControllerPakType;
 
 		/// <summary>
 		/// Connects and disconnects controllers
@@ -50,7 +50,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 		/// <param name="connected">1 if controller should be connected, 0 if controller should be disconnected</param>
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		delegate void SetControllerConnected(int controller, int connected);
-		SetControllerConnected InpSetControllerConnected;
+		readonly SetControllerConnected InpSetControllerConnected;
 
 		/// <summary>
 		/// Event fired when mupen changes rumble pak status

src/BizHawk.Emulation.Cores/Consoles/Nintendo/N64/NativeApi/mupen64plusVideoApi.cs

@@ -18,7 +18,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 		/// <param name="buffer">Which buffer to read: 0 = front, 1 = back</param>
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		private delegate void ReadScreen2(int[] framebuffer, ref int width, ref int height, int buffer);
-		ReadScreen2 GFXReadScreen2;
+		readonly ReadScreen2 GFXReadScreen2;
 
 		/// <summary>
 		/// Gets the width and height of the mupen64plus framebuffer
@@ -29,9 +29,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64.NativeApi
 		/// <param name="buffer">Which buffer to read: 0 = front, 1 = back</param>
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		private delegate void ReadScreen2Res(IntPtr dummy, ref int width, ref int height, int buffer);
-		ReadScreen2Res GFXReadScreen2Res;
+		readonly ReadScreen2Res GFXReadScreen2Res;
 
-		
 		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 		private delegate int GetScreenTextureID();
 		GetScreenTextureID GFXGetScreenTextureID;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/APU.cs

@@ -26,7 +26,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		public bool recalculate = false;
 
-		NES nes;
+		readonly NES nes;
 		public APU(NES nes, APU old, bool pal)
 		{
 			this.nes = nes;
@@ -43,25 +43,25 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			}
 		}
 
-		static int[] DMC_RATE_NTSC = { 428, 380, 340, 320, 286, 254, 226, 214, 190, 160, 142, 128, 106, 84, 72, 54 };
+		static readonly int[] DMC_RATE_NTSC = { 428, 380, 340, 320, 286, 254, 226, 214, 190, 160, 142, 128, 106, 84, 72, 54 };
-		static int[] DMC_RATE_PAL = { 398, 354, 316, 298, 276, 236, 210, 198, 176, 148, 132, 118, 98, 78, 66, 50 };
+		static readonly int[] DMC_RATE_PAL = { 398, 354, 316, 298, 276, 236, 210, 198, 176, 148, 132, 118, 98, 78, 66, 50 };
-		static int[] LENGTH_TABLE = { 10, 254, 20, 2, 40, 4, 80, 6, 160, 8, 60, 10, 14, 12, 26, 14, 12, 16, 24, 18, 48, 20, 96, 22, 192, 24, 72, 26, 16, 28, 32, 30 };
+		static readonly int[] LENGTH_TABLE = { 10, 254, 20, 2, 40, 4, 80, 6, 160, 8, 60, 10, 14, 12, 26, 14, 12, 16, 24, 18, 48, 20, 96, 22, 192, 24, 72, 26, 16, 28, 32, 30 };
-		static byte[,] PULSE_DUTY = {
+		static readonly byte[,] PULSE_DUTY = {
 			{0,1,0,0,0,0,0,0}, // (12.5%)
 			{0,1,1,0,0,0,0,0}, // (25%)
 			{0,1,1,1,1,0,0,0}, // (50%)
 			{1,0,0,1,1,1,1,1}, // (25% negated (75%))
 		};
-		static byte[] TRIANGLE_TABLE =
+		static readonly byte[] TRIANGLE_TABLE =
 		{
 			15, 14, 13, 12, 11, 10,  9,  8,  7,  6,  5,  4,  3,  2,  1,  0,
 			0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15
 		};
-		static int[] NOISE_TABLE_NTSC =
+		static readonly int[] NOISE_TABLE_NTSC =
 		{
 			4, 8, 16, 32, 64, 96, 128, 160, 202, 254, 380, 508, 762, 1016, 2034, 4068
 		};
-		static int[] NOISE_TABLE_PAL =
+		static readonly int[] NOISE_TABLE_PAL =
 		{
 			4, 7, 14, 30, 60, 88, 118, 148, 188, 236, 354, 472, 708,  944, 1890, 3778
 		};
@@ -70,7 +70,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		{
 			public PulseUnit(APU apu, int unit) { this.unit = unit; this.apu = apu; }
 			public int unit;
-			APU apu;
+			readonly APU apu;
 
 			// reg0
 			int duty_cnt, env_loop, env_constant, env_cnt_value;
@@ -309,7 +309,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		public sealed class NoiseUnit
 		{
-			APU apu;
+			readonly APU apu;
 
 			// reg0 (sweep)
 			int env_cnt_value, env_loop, env_constant;
@@ -331,7 +331,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			int env_output, env_start_flag, env_divider, env_counter;
 			bool noise_bit = true;
 
-			int[] NOISE_TABLE;
+			readonly int[] NOISE_TABLE;
 
 			public NoiseUnit(APU apu, bool pal)
 			{
@@ -508,7 +508,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			int seq = 0;
 			public int sample;
 
-			APU apu;
+			readonly APU apu;
 			public TriangleUnit(APU apu) { this.apu = apu; }
 
 			public void SyncState(Serializer ser)
@@ -648,8 +648,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		sealed class DMCUnit
 		{
-			APU apu;
+			readonly APU apu;
-			int[] DMC_RATE;
+			readonly int[] DMC_RATE;
 			public DMCUnit(APU apu, bool pal)
 			{
 				this.apu = apu;
@@ -940,7 +940,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		public PulseUnit[] pulse = new PulseUnit[2];
 		public TriangleUnit triangle;
 		public NoiseUnit noise;
-		DMCUnit dmc;
+		readonly DMCUnit dmc;
 
 		bool irq_pending;
 		bool dmc_irq;
@@ -959,14 +959,14 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			dmc.Fetch();
 		}
 
-		int[][] sequencer_lut = new int[2][];
+		readonly int[][] sequencer_lut = new int[2][];
 
-		static int[][] sequencer_lut_ntsc = {
+		static readonly int[][] sequencer_lut_ntsc = {
 			new[]{7457,14913,22371,29830},
 			new[]{7457,14913,22371,29830,37282}
 		};
 
-		static int[][] sequencer_lut_pal = {
+		static readonly int[][] sequencer_lut_pal = {
 			new[]{8313,16627,24939,33254},
 			new[]{8313,16627,24939,33254,41566}
 		};

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/BANDAI-FCG-1.cs

@@ -42,7 +42,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		byte jump2_outer_bank; // needed to select between banks in 512K jump2 board
 
 		//regenerable state
-		int[] prg_banks_16k = new int[2];
+		readonly int[] prg_banks_16k = new int[2];
 
 		//state
 		int prg_reg_16k;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/GameGenie.cs

@@ -6,7 +6,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 	internal sealed class GameGenie : NesBoardBase
 	{
-		static byte[] PatternTables = new byte[256];
+		static readonly byte[] PatternTables = new byte[256];
 
 		static GameGenie()
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper114.cs

@@ -9,7 +9,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		private int prg_mask_16;
 
-		private byte[] sec = { 0, 3, 1, 5, 6, 7, 2, 4 };
+		private readonly byte[] sec = { 0, 3, 1, 5, 6, 7, 2, 4 };
 
 		public override bool Configure(EDetectionOrigin origin)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper123.cs

@@ -7,7 +7,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 	{
 		private byte[] EXPREGS = new byte[8];
 
-		private byte[] sec = { 0, 3, 1, 5, 6, 7, 2, 4 };
+		private readonly byte[] sec = { 0, 3, 1, 5, 6, 7, 2, 4 };
 
 		public override bool Configure(EDetectionOrigin origin)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper182.cs

@@ -41,11 +41,11 @@
 			}
 		}
 
-		static byte[] scramble_table = { 0, 3, 1, 5, 6, 7, 2, 4 };
+		static readonly byte[] scramble_table = { 0, 3, 1, 5, 6, 7, 2, 4 };
-		static int scramble_A000(byte val)
+
+		private static int scramble_A000(byte val)
 		{
 			return (val & ~0x7) | scramble_table[val & 0x7];
 		}
-
 	}
 }

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper215.cs

@@ -12,7 +12,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		private int prg_mask_8k, chr_mask_1k;
 
-		private byte[] regs_sec = { 0, 2, 5, 3, 6, 1, 7, 4 }; 
+		private readonly byte[] regs_sec = { 0, 2, 5, 3, 6, 1, 7, 4 }; 
 
 		/*
 		 *  I'm not sure where these matrices originated from, but they don't seem to be needed

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper217.cs

@@ -8,7 +8,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		public byte[] prg_regs_8k = new byte[4];
 		private int prg_mask_8k, chr_mask_1k;
-		private byte[] regs_sec = { 0, 6, 3, 7, 5, 2, 4, 1 };
+		private readonly byte[] regs_sec = { 0, 6, 3, 7, 5, 2, 4, 1 };
 
 
 		public override bool Configure(EDetectionOrigin origin)

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/MMC3_family/Pocahontas.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		private int prg_mask_8k, chr_mask_1k;
 
-		private byte[] regs_sec = { 0, 2, 6, 1, 7, 3, 4, 5 }; 
+		private readonly byte[] regs_sec = { 0, 2, 6, 1, 7, 3, 4, 5 }; 
 
 		public override bool Configure(EDetectionOrigin origin)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper043.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		bool swap;
 
 
-		private static int[] lut = { 4, 3, 5, 3, 6, 3, 7, 3 };
+		private static readonly int[] lut = { 4, 3, 5, 3, 6, 3, 7, 3 };
 
 		public override bool Configure(EDetectionOrigin origin)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper116.cs

@@ -33,7 +33,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 				master.SyncIRQ(flag);
 			}
 
-			Mapper116 master;
+			readonly Mapper116 master;
 
 		}
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper156.cs

@@ -14,7 +14,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		int prg_mask;
 		int chr_mask;
 		int prg;
-		int[] chr = new int[8];
+		readonly int[] chr = new int[8];
 
 		public override bool Configure(EDetectionOrigin origin)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper244.cs

@@ -18,7 +18,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			return true;
 		}
 
-		private List<List<byte>> prg_perm = new List<List<byte>>
+		private readonly List<List<byte>> prg_perm = new List<List<byte>>
 		{
 			new List<byte> { 0, 1, 2, 3, },
 			new List<byte> { 3, 2, 1, 0, },
@@ -26,7 +26,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			new List<byte> { 3, 1, 2, 0, },
 		};
 
-		private List<List<byte>> chr_perm = new List<List<byte>>
+		private readonly List<List<byte>> chr_perm = new List<List<byte>>
 		{
 			new List<byte> { 0, 1, 2, 3, 4, 5, 6, 7, },
 			new List<byte> { 0, 2, 1, 3, 4, 6, 5, 7, },

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/NSFBoard.cs

@@ -33,12 +33,12 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		/// <summary>
 		/// the bankswitch values to be used before the INIT routine is called
 		/// </summary>
-		byte[] InitBankSwitches = new byte[8];
+		readonly byte[] InitBankSwitches = new byte[8];
 
 		/// <summary>
 		/// An image of the entire PRG space where the unmapped files are located
 		/// </summary>
-		byte[] FakePRG = new byte[32768];
+		readonly byte[] FakePRG = new byte[32768];
 
 		//------------------------------
 		//state
@@ -240,7 +240,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		//3FF3 - PatchVectors=false
 		//3FF4 - PatchVectors=true
 
-		byte[] NSFROM = new byte[0x23]
+		readonly byte[] NSFROM = new byte[0x23]
 		{
 			//@NMIVector
 			//Suspend vector patching

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Namcot129_163.cs

@@ -23,7 +23,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		//state
 		int[] prg_banks_8k = new int[4];
 		int[] chr_banks_1k = new int[12];
-		bool[] vram_enable = new bool[3];
+		readonly bool[] vram_enable = new bool[3];
 
 		int irq_counter;
 		bool irq_enabled;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Namcot1xx/Namco163Audio.cs

@@ -102,7 +102,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			ser.Sync(nameof(ch), ref ch);
 		}
 
-		Action<int> enqueuer;
+		readonly Action<int> enqueuer;
 
 		public Namco163Audio(Action<int> enqueuer)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Namcot1xx/Namcot1xx.cs

@@ -96,7 +96,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		// security reading index for tko boxing
 		int tko_security = 0;
-		static byte[] TKO = { 0xFF, 0xBF, 0xB7, 0x97, 0x97, 0x17, 0x57, 0x4F, 0x6F, 0x6B, 0xEB, 0xA9, 0xB1, 0x90, 0x94, 0x14,
+		static readonly byte[] TKO = { 0xFF, 0xBF, 0xB7, 0x97, 0x97, 0x17, 0x57, 0x4F, 0x6F, 0x6B, 0xEB, 0xA9, 0xB1, 0x90, 0x94, 0x14,
 										 0x56, 0x4E, 0x6F, 0x6B, 0xEB, 0xA9, 0xB1, 0x90, 0xD4, 0x5C, 0x3E, 0x26, 0x87, 0x83, 0x13, 0x51};
 
 		public override void SyncState(Serializer ser)

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/PxROM_FxROM.cs

@@ -13,7 +13,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		//state
 		byte prg_reg;
-		int[] prg_banks_8k = new int[4];
+		readonly int[] prg_banks_8k = new int[4];
 		int[] chr_banks_4k = new int[4];
 		int[] chr_latches = new int[2];
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/SEEPROM.cs

@@ -16,7 +16,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		/// <summary>
 		/// true if 256byte
 		/// </summary>
-		bool Big;
+		readonly bool Big;
 
 		byte[] rom;
 		/// <summary>aux circuitry? D7 of data byte</summary>

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/TENGEN-800032.cs

@@ -6,18 +6,20 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 	//AKA mapper 64
 	internal sealed class TENGEN_800032 : NesBoardBase
 	{
-		//configuration
+		// configuration
 		int prg_bank_mask_8k;
 		int chr_bank_mask_1k;
 
-		//regenerable state
+		// regenerable state
-		int[] prg_banks_8k = new int[4];
+		readonly int[] prg_banks_8k = new int[4];
-		int[] chr_banks_1k = new int[8];
+		readonly int[] chr_banks_1k = new int[8];
-		//state
+		
+		// state
 		int[] regs = new int[16];
 		int address;
 		bool chr_1k, chr_mode, prg_mode;
-		//irq
+		
+		// irq
 		int irq_countdown;
 		int a12_old;
 		int irq_reload, irq_counter;
@@ -191,7 +193,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			return Rom[addr];
 		}
 
-
 		public override byte ReadPpu(int addr)
 		{
 			if (addr < 0x2000)
@@ -328,6 +329,5 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 			a12_old = a12;
 		}
-
 	}
 }

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Taito_X1_017.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		private byte[] prg_regs_8k = new byte[4];
 		private byte[] chr_regs_1k = new byte[8];
 		private bool ChrMode;
-		private bool[] wramenable = new bool[3];
+		private readonly bool[] wramenable = new bool[3];
 
 		public override void SyncState(Serializer ser)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/UNIF/UNIF_BMC-D1038.cs

@@ -14,7 +14,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		private int _reg;
 
-		private int DipswitchMask = 3;
+		private readonly int DipswitchMask = 3;
 
 		private bool Prg16kMode => _reg.Bit(7);
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/UNIF/UNIF_BMC-GS-2013.cs

@@ -11,11 +11,11 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		private int _reg = 0xFF;
 		private bool _isRom2 = true;
 
-		private int _prgMaskRom1 = 7;
+		private readonly int _prgMaskRom1 = 7;
-		private int _prgMaskRom2 = 1;
+		private readonly int _prgMaskRom2 = 1;
 
-		private int _wramPage = 0x3E000;
+		private readonly int _wramPage = 0x3E000;
-		private int _rom2Offset = 0x40000;
+		private readonly int _rom2Offset = 0x40000;
 
 		public override bool Configure(EDetectionOrigin origin)
 		{

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/UNIF/UNIF_UNL_DripGame.cs

@@ -300,7 +300,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			int latched;
 
 			// communicate with APU
-			Action<int> enqueuer;
+			readonly Action<int> enqueuer;
 			// true if V has been written and we need to check to change something
 			bool volumeChangePending;
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/VRC1.cs

@@ -13,7 +13,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		//state
 		int[] prg_banks_8k = new int[4];
 		int[] chr_banks_4k = new int[2];
-		int[] chr_regs_4k = new int[2];
+		readonly int[] chr_regs_4k = new int[2];
 
 		//the VS actually does have 2 KB of nametable address space
 		//let's make the extra space here, instead of in the main NES to avoid confusion

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/VRC2_4.cs

@@ -66,7 +66,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		private bool extrabig_chr = false;
 
 		//state
-		private int[] prg_bank_reg_8k = new int[2];
+		private readonly int[] prg_bank_reg_8k = new int[2];
 		public int[] chr_bank_reg_1k = new int[16];
 		private bool _prgMode;
 		public byte[] prg_banks_8k = new byte[4];

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/VRC6.cs

@@ -13,11 +13,11 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		// what did i do in a previous life to deserve this?
 
 		// given the bottom four bits of $b003, and a 1K address region in PPU $0000:$3fff,
-		static byte[] Banks = new byte[16 * 16]; // which of the 8 chr regs is used to determine the bank here?
+		static readonly byte[] Banks = new byte[16 * 16]; // which of the 8 chr regs is used to determine the bank here?
-		static byte[] Masks = new byte[16 * 16]; // what is the resulting 8 bit chr reg value ANDed with?
+		static readonly byte[] Masks = new byte[16 * 16]; // what is the resulting 8 bit chr reg value ANDed with?
-		static byte[] A10s = new byte[16 * 16]; // and then what is it ORed with?
+		static readonly byte[] A10s = new byte[16 * 16]; // and then what is it ORed with?
 
-		static byte[] PTables = 
+		static readonly byte[] PTables = 
 		{
 			0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,
 			0x80,0xc0,0x81,0xc1,0x82,0xc2,0x83,0xc3,
@@ -113,7 +113,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		//state
 		int prg_bank_16k, prg_bank_8k;
-		byte[] prg_banks_8k = new byte[4];
+		readonly byte[] prg_banks_8k = new byte[4];
 		byte[] chr_banks_1k = new byte[8];
 		bool irq_mode;
 		bool irq_enabled, irq_pending, irq_autoen;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/BootGodDB.cs

@@ -10,12 +10,12 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 {
 	public class BootGodDb
 	{
-		/// <summary>
+		/// <summary>
-		/// blocks until the DB is done loading
+		/// blocks until the DB is done loading
-		/// </summary>
+		/// </summary>
 		static EventWaitHandle acquire;
 
-		bool validate = true;
+		readonly bool validate = true;
 
 		private readonly Bag<string, CartInfo> _sha1Table = new Bag<string, CartInfo>();
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/FDSAudio.cs

@@ -146,7 +146,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		int latchedoutput;
 
-		Action<int> SendDiff;
+		readonly Action<int> SendDiff;
 
 		public FDSAudio(Action<int> SendDiff)
 		{