From b28ab42e18043e9a637494000cb2b9e3dbcf4b29 Mon Sep 17 00:00:00 2001
From: saxxonpike <saxxonpike@gmail.com>
Date: Sat, 10 Nov 2012 07:42:05 +0000
Subject: [PATCH] commodore64: VIC now only sees character rom at $1000 and
 $9000

---
 .../Computers/Commodore64/MemBus.cs           | 51 +++++++++++--------
 .../Computers/Commodore64/VicII.cs            |  2 +-
 2 files changed, 30 insertions(+), 23 deletions(-)

diff --git a/BizHawk.Emulation/Computers/Commodore64/MemBus.cs b/BizHawk.Emulation/Computers/Commodore64/MemBus.cs
index e4c4b0799b..c861dfdf29 100644
--- a/BizHawk.Emulation/Computers/Commodore64/MemBus.cs
+++ b/BizHawk.Emulation/Computers/Commodore64/MemBus.cs
@@ -55,10 +55,10 @@ namespace BizHawk.Emulation.Computers.Commodore64
 		public MemoryLayout layout;
 
 		// ram
-		public byte cia2A;
-		public byte cia2B;
 		public byte[] colorRam;
 		public byte[] ram;
+		public bool vicCharEnabled;
+		public ushort vicOffset;
 
 		// registers
 		public byte busData;
@@ -98,7 +98,7 @@ namespace BizHawk.Emulation.Computers.Commodore64
 			cia1 = newCia1;
 			cia1.ports[0] = cia1PortA;
 			cia1.ports[1] = cia1PortB;
-
+			cia1PortA.WritePort = UpdateVicOffset;
 			HardReset();
 		}
 
@@ -191,6 +191,7 @@ namespace BizHawk.Emulation.Computers.Commodore64
 			cpuPort = new DirectionalDataPort(0x37, 0x2F);
 			layout = new MemoryLayout();
 			UpdateLayout();
+			UpdateVicOffset(cia1PortA.Data);
 		}
 
 		public byte Peek(ushort addr)
@@ -423,33 +424,39 @@ namespace BizHawk.Emulation.Computers.Commodore64
 			}
 		}
 
+		private void UpdateVicOffset(byte val)
+		{
+			switch (cia1PortA.Data & 0x03)
+			{
+				case 0:
+					vicCharEnabled = false;
+					vicOffset = 0xC000;
+					break;
+				case 1:
+					vicCharEnabled = true;
+					vicOffset = 0x8000;
+					break;
+				case 2:
+					vicCharEnabled = false;
+					vicOffset = 0x4000;
+					break;
+				default:
+					vicCharEnabled = true;
+					vicOffset = 0x0000;
+					break;
+			}
+		}
+
 		public byte VicRead(ushort addr)
 		{
 			addr = (ushort)(addr & 0x3FFF);
-			if (addr >= 0x1000 && addr < 0x2000)
+			if (vicCharEnabled && (addr >= 0x1000 && addr < 0x2000))
 			{
 				return charRom[addr & 0x0FFF];
 			}
 			else
 			{
-				int baseAddr = 0;
-				int videoOffsetIndex = cia1PortA.Data & 0x03;
-				switch (videoOffsetIndex)
-				{
-					case 0:
-						baseAddr = 0xC000 | addr;
-						break;
-					case 1:
-						baseAddr = 0x8000 | addr;
-						break;
-					case 2:
-						baseAddr = 0x4000 | addr;
-						break;
-					default:
-						baseAddr = addr;
-						break;
-				}
-				return ram[(ushort)baseAddr];
+				return ram[addr | vicOffset];
 			}
 		}
 
diff --git a/BizHawk.Emulation/Computers/Commodore64/VicII.cs b/BizHawk.Emulation/Computers/Commodore64/VicII.cs
index b924f46568..1e07796bd3 100644
--- a/BizHawk.Emulation/Computers/Commodore64/VicII.cs
+++ b/BizHawk.Emulation/Computers/Commodore64/VicII.cs
@@ -1109,7 +1109,7 @@ namespace BizHawk.Emulation.Computers.Commodore64
 							else
 							{
 								spriteBits = (int)((regs.MSR[j] >> 30) & 0x2);
-								if ((!regs.MxXE[j]) || (rasterOffsetX & 0x1) != (regs.MxX[j] & 0x1))
+								if ((!regs.MxXE[j]) || ((rasterOffsetX & 0x1) != (regs.MxX[j] & 0x1)))
 								{
 									regs.MSR[j] <<= 1;
 									regs.MSRC[j]--;