From 3bf90c5e42f9813041a4ac66314e89695777b246 Mon Sep 17 00:00:00 2001
From: alyosha-tas <alexei.f.k@gmail.com>
Date: Sat, 29 Oct 2016 18:54:34 -0400
Subject: [PATCH] Update VRC-1 to run VS system game mirroring modes

---
 .../Consoles/Nintendo/NES/Boards/VRC1.cs      | 55 ++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/VRC1.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/VRC1.cs
index b33dc810a5..b093226c55 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/VRC1.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/VRC1.cs
@@ -1,5 +1,6 @@
 using BizHawk.Common;
 using BizHawk.Common.NumberExtensions;
+using System;
 
 namespace BizHawk.Emulation.Cores.Nintendo.NES
 {
@@ -15,6 +16,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 		IntBuffer chr_banks_4k = new IntBuffer(2);
 		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
+		byte[] CIRAM_VS = new byte[0x800];
+
 		public override void Dispose()
 		{
 			base.Dispose();
@@ -27,6 +32,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			base.SyncState(ser);
 			ser.Sync("prg_banks_8k", ref prg_banks_8k);
 			ser.Sync("chr_banks_4k", ref chr_banks_4k);
+			ser.Sync("VS_CIRAM", ref CIRAM_VS, false);
 			for (int i = 0; i < 2; i++) ser.Sync("chr_regs_4k_" + i, ref chr_regs_4k[i]);
 
 			if (ser.IsReader)
@@ -82,7 +88,54 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 				addr = (bank_4k << 12) | ofs;
 				return VROM[addr];
 			}
-			else return base.ReadPPU(addr);
+			else
+			{
+				if (NES._isVS)
+				{
+					addr = addr - 0x2000;
+					if (addr < 0x800)
+					{
+						return NES.CIRAM[addr];
+					}
+					else
+					{
+						return CIRAM_VS[addr - 0x800];
+					}
+				}			
+				else
+					return base.ReadPPU(addr);
+			}
+			
+		}
+
+		public override void WritePPU(int addr, byte value)
+		{
+			// The game VS Goonies apparently scans for more CIRAM then actually exists, so we have to mask out nonsensical values 
+			addr &= 0x2FFF;
+
+			if (NES._isVS)
+			{
+				if (addr < 0x2000)
+				{
+					if (VRAM != null)
+						VRAM[addr] = value;
+				}
+				else
+				{
+					Console.WriteLine(addr);
+					addr = addr - 0x2000;
+					if (addr < 0x800)
+					{
+						NES.CIRAM[addr] = value;
+					}
+					else
+					{
+						CIRAM_VS[addr - 0x800] = value;
+					}
+				}
+			}
+			else
+				base.WritePPU(addr, value);
 		}
 
 		void SyncCHR()