diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper164.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper164.cs
index c474459a24..e141344429 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper164.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper164.cs
@@ -7,11 +7,42 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 {
 	class Mapper164 : NES.NESBoardBase 
 	{
-		//Mapper 164
-		//Final Fantasy V (Unl)
+		/*
+		* Here are Disch's original notes:  
+		========================
+		=  Mapper 164          =
+		========================
+ 
+		Example Game:
+		--------------------------
+		Final Fantasy V
+ 
+ 
+ 
+		Registers:
+		---------------------------
+ 
+		Range,Mask:   $5000-FFFF, $F300
+ 
+		$5000, $D000:  PRG reg (32k @ $8000)
+ 
+		$6000-7FFF may have SRAM (not sure)
+ 
+ 
+		On Reset
+		---------------------------
+		Reg seems to contain $FF on powerup/reset
+ 
+ 
+		Notes:
+		---------------------------
+ 
+		Swapping is really simple -- the thing that is funky is the register range/mask.  $5000 and $D000 will access
+		the register, however $5100, $5200, etc will not.
+		*/
 
-		//state
-		int prg;
+		int prg_bank;
+		int prg_bank_mask_32k;
 
 		public override bool Configure(NES.EDetectionOrigin origin)
 		{
@@ -22,34 +53,40 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 				default:
 					return false;
 			}
-			SetMirrorType(Cart.pad_h, Cart.pad_v);
-			prg = 0xFF;
+			prg_bank = 0xFF;
+			prg_bank_mask_32k = Cart.prg_size / 32 - 1;
 			return true;
 		}
 
 		public override void WriteEXP(int addr, byte value)
 		{
-			addr &= 0xF300;
-			if (addr == 0x5000)
-				prg = value;
+			addr = (addr + 0x4000) & 0xF300;
+			if (addr == 0x5000 || addr == 0xD000)
+				prg_bank = value;
 		}
 
 		public override void WritePRG(int addr, byte value)
 		{
-			addr &= 0xF300;
-			if (addr == 0xD000)
-				prg = value;
+			addr = (addr + 0x8000) & 0xF300;
+			if (addr == 0x5000 || addr == 0xD000)
+				prg_bank = value;
 		}
 
-		public override byte ReadPPU(int addr)
+		public override byte ReadPRG(int addr)
 		{
-			return VROM[addr + (prg * 0x8000)];
+			return ROM[addr + ((prg_bank & prg_bank_mask_32k) * 0x8000)];
 		}
 
 		public override void SyncState(Serializer ser)
 		{
 			base.SyncState(ser);
-			ser.Sync("prg", ref prg);
+			ser.Sync("prg", ref prg_bank);
+		}
+
+		public override void NESSoftReset()
+		{
+			prg_bank = 0xFF;
+			base.NESSoftReset();
 		}
 	}
 }