diff --git a/src/boards/598.c b/src/boards/598.c
index 63c0274..c109155 100644
--- a/src/boards/598.c
+++ b/src/boards/598.c
@@ -20,28 +20,27 @@
 
 #include "mapinc.h"
 
-static uint8 reg[4];
+static uint8 reg[2];
 
 static void sync () {
-	int prg = reg[3] <<3 | reg[1] &0x07;
-	if (reg[3] &0x08)
-		setprg32(0x8000, prg >>1);
-	else {
-		setprg16(0x8000, prg);
-		setprg16(0xC000, prg |7);
+	setprg16(0x8000, reg[0] &0x18 | reg[1] &0x07);
+	setprg16(0xC000, reg[0] &0x18 |         0x07);
+	setchr8(0);
+	switch(reg[0] &0x03) {
+		case 0x00: setmirror(MI_0); break;
+		case 0x01: setmirror(MI_V); break;
+		case 0x02: setmirror(MI_H); break;
+		case 0x03: setmirror(MI_1); break;
 	}
-	setchr4(0x0000, reg[3] <<5 | reg[1] >>3 &0x1F);
-	setchr4(0x1000, reg[3] <<5 | reg[2] >>3 &0x1F);
-	setmirror(reg[3] &0x04? MI_H: MI_V);
 }
 
 static DECLFW (writeReg) {
-	reg[A >>13 &3] = V;
+	reg[A >>14 &1] = V;
 	sync();
 }
 
 static void reset () {
-	reg[0] = reg[1] = reg[2] = reg[3] = 0;
+	reg[0] = reg[1] = 0;
 	sync();
 }
 
@@ -59,5 +58,5 @@ void Mapper598_Init (CartInfo *info) {
 	info->Power = power;
 	info->Reset = reset;
 	GameStateRestore = stateRestore;
-	AddExState(reg, 4, 0, "REGS");
+	AddExState(reg, 2, 0, "REGS");
 }
diff --git a/src/ines.c b/src/ines.c
index 699cda9..1a9b070 100644
--- a/src/ines.c
+++ b/src/ines.c
@@ -1019,6 +1019,7 @@ INES_BOARD_BEGIN()
 	INES_BOARD( "4MROM-512",                595, Mapper595_Init         )
 	INES_BOARD( "FC-49",                    596, Mapper596_Init         )
 	INES_BOARD( "GN-27",                    597, Mapper597_Init         )
+	INES_BOARD( "3936",                     598, Mapper598_Init         )
 INES_BOARD_END()
 
 static uint32 iNES_get_mapper_id(void)
diff --git a/src/ines.h b/src/ines.h
index 78674eb..b5adf55 100644
--- a/src/ines.h
+++ b/src/ines.h
@@ -488,7 +488,7 @@ void Mapper594_Init(CartInfo *);
 void Mapper595_Init(CartInfo *);
 void Mapper596_Init(CartInfo *);
 void Mapper597_Init(CartInfo *);
-
+void Mapper598_Init(CartInfo *);
 void FFE_Init(CartInfo *);
 
 #endif