[NES] add GxROM

BizHawk.Emulation/BizHawk.Emulation.csproj

@@ -58,6 +58,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\AxROM.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\CPROM.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\CxROM.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\GxROM.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\IC_74x377.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\NROM.cs" />
     <Compile Include="Consoles\Nintendo\NES\BoardDetector.cs" />

BizHawk.Emulation/Consoles/Nintendo/NES/BoardDetector.cs

@@ -49,6 +49,8 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 11	4	2	Discrete_74x377
 11	2	4	Discrete_74x377
 13	2	0	CPROM
+66	4	2	GxROM
+66	8	4	GxROM
 ";
 
 		}

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/AxROM.cs

@@ -55,12 +55,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo.Boards
 
 		public override void WritePRG(int addr, byte value)
 		{
-			if (bus_conflict)
+			if (bus_conflict) value = HandleNormalPRGConflict(addr,value);
-			{
-				byte old_value = value;
-				value &= ReadPRG(addr);
-				Debug.Assert(old_value == value, "Found a test case of CxROM bus conflict. please report.");
-			}
 			prg = value & prg_mask;
 			if ((value & 0x10) == 0)
 				SetMirrorType(NES.EMirrorType.OneScreenA);

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/CxROM.cs

@@ -22,12 +22,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo.Boards
 		
 		public override void WritePRG(int addr, byte value)
 		{
-			if (bus_conflict)
+			if (bus_conflict) value = HandleNormalPRGConflict(addr,value);
-			{
-				byte old_value = value;
-				value &= ReadPRG(addr);
-				Debug.Assert(old_value == value,"Found a test case of CxROM bus conflict. please report.");
-			}
 			chr = value&chr_mask;
 			//Console.WriteLine("at {0}, set chr={1}", NES.ppu.ppur.status.sl, chr);
 		}

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/GxROM.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Diagnostics;
+
+namespace BizHawk.Emulation.Consoles.Nintendo.Boards
+{
+	public class GxROM : NES.NESBoardBase
+	{
+		int prg_mask, chr_mask;
+		int prg, chr;
+
+		public override void Initialize(NES.RomInfo romInfo, NES nes)
+		{
+			base.Initialize(romInfo, nes);
+			Debug.Assert(romInfo.PRG_Size == 2 || romInfo.PRG_Size == 4 || romInfo.PRG_Size == 8);
+			//romInfo.CHR_Size == 8 || romInfo.CHR_Size == 16
+			Debug.Assert(romInfo.CHR_Size == 2 || romInfo.CHR_Size == 4, "This is unverified behaviour. Please check it (maybe you are playing thunder&lightning; do you have to play far into that game to see missing CHR?");
+
+			prg_mask = (romInfo.PRG_Size/2) - 1;
+			chr_mask = romInfo.CHR_Size - 1;
+		}
+		public override byte ReadPRG(int addr)
+		{
+			return RomInfo.ROM[addr + (prg<<15)];
+		}
+
+		public override byte ReadPPU(int addr)
+		{
+			if (addr < 0x2000)
+			{
+				return RomInfo.VROM[addr + (chr << 13)];
+			}
+			else return base.ReadPPU(addr);
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			chr = ((value & 3) & chr_mask);
+			prg = (((value>>4) & 3) & prg_mask);
+		}
+
+		int mask;
+	}
+}

BizHawk.Emulation/Consoles/Nintendo/NES/NES.cs

@@ -645,6 +645,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 					case "AOROM": board = new Boards.AxROM("AOROM"); break;
 					case "Discrete_74x377": board = new Boards.Discrete_74x377(); break;
 					case "CPROM": board = new Boards.CPROM(); break;
+					case "GxROM": board = new Boards.GxROM(); break;	
 				}
 
 				if (board == null) throw new InvalidOperationException("Couldn't classify NES rom");