From 2278cfcccbac11b31dc8172e9f8ca9deb9c23eb9 Mon Sep 17 00:00:00 2001
From: zeromus <zeromus@zeromus.org>
Date: Tue, 6 Mar 2012 19:19:56 +0000
Subject: [PATCH] nes-fix $2007 access while rendering (young indiana jones)

---
 .../Consoles/Nintendo/NES/PPU.regs.cs         | 24 ++++++++++++-------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/PPU.regs.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/PPU.regs.cs
index a380d8087d..6c498bc6d2 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/NES/PPU.regs.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/PPU.regs.cs
@@ -60,6 +60,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			public struct PPUSTATUS
 			{
 				public int sl;
+				public bool rendering { get { return sl >= 0 && sl < 241; } }
 				public int cycle, end_cycle;
 			}
 
@@ -224,8 +225,16 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 					return (s << 0xC) | (par << 0x4) | fv;
 				}
 
-				public void increment2007(bool by32)
+				public void increment2007(bool rendering, bool by32)
 				{
+					//new knowledge as of 2010 - use this incrementing method while rendering is active (thanks, nemulator)
+					//http://nesdev.parodius.com/bbs/viewtopic.php?t=6401
+					if (rendering)
+					{
+						if (by32) increment_vs();
+						else increment_hsc();
+						return;
+					}
 
 					//If the VRAM address increment bit (2000.2) is clear (inc. amt. = 1), all the
 					//scroll counters are daisy-chained (in the order of HT, VT, H, V, FV) so that
@@ -458,9 +467,9 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 					ppubus_write(addr, value);
 				}
 
-				ppur.increment2007(reg_2000.vram_incr32 != 0);
-				int newaddr = ppur.get_2007access() & 0x3FFF;
-				nes.board.AddressPPU(newaddr);
+				nes.board.AddressPPU(addr);
+
+				ppur.increment2007(ppur.status.rendering && reg_2001.PPUON, reg_2000.vram_incr32 != 0);
 			}
 			byte read_2007()
 			{
@@ -479,11 +488,10 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 					ret = PALRAM[addr & 0x1F];
 				}
 
-				ppur.increment2007(reg_2000.vram_incr32 != 0);
-				
-				int newaddr = ppur.get_2007access() & 0x3FFF;
-				nes.board.AddressPPU(newaddr);
+				nes.board.AddressPPU(addr);
 
+				ppur.increment2007(ppur.status.rendering && reg_2001.PPUON, reg_2000.vram_incr32 != 0);
+				
 				return ret;
 			}
 			//--------