diff --git a/Docs/smstech.txt b/Docs/smstech.txt
index ed86d32..baa3486 100644
--- a/Docs/smstech.txt
+++ b/Docs/smstech.txt
@@ -194,7 +194,7 @@
            Writes to odd addresses go to the VDP control port.
            Reads from even addresses return the VDP data port contents.
            Reads from odd address return the VDP status flags.
- $C0-$FF : Writes have no effect.
+ $C0-$FF : Writes have no effect, except 0xF2 which goes to the YM2413.
            Reads from even addresses return the I/O port A/B register.
            Reads from odd address return the I/O port B/misc. register.
 
diff --git a/History.txt b/History.txt
index 9c9037b..07e50bf 100644
--- a/History.txt
+++ b/History.txt
@@ -2,6 +2,10 @@ S8DS revision history
 -=-=-=-=-=-=-=-=-=-=-=-
 
 
+V1.1.3 - 2021-10-12 (FluBBa)
+	Fixed crash at startup.
+	Added ui to enable/disable YM2413.
+
 V1.1.2 - 2021-10-11 (FluBBa)
 	Fixed TV noise.
 
diff --git a/README.md b/README.md
index 142512d..b1e72a4 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# S8DS V1.1.2
+# S8DS V1.1.3
 
 This is a SEGA 8Bit emulator for the NDS, it support the following systems:
 
@@ -96,6 +96,7 @@ better 3D effect, I have only tested with red/cyan glasses.
 			Select GameGear Bios: Browse for GameGear bios.
 			Select Coleco Bios: Browse for Coleco bios.
 			Select MSX Bios: Browse for MSX bios.
+		YM2413: Enable YM2413 emulation for SMS1 & Mark 3.
 
 	Settings:
 		Speed: Switch between speed modes, can also be toggled with L+START.
diff --git a/source/Cart.s b/source/Cart.s
index fe4f759..153b073 100644
--- a/source/Cart.s
+++ b/source/Cart.s
@@ -217,7 +217,7 @@ loadCart: 		;@ Called from C:  r0=emuFlags
 
 	ldr z80optbl,=Z80OpTable
 
-	ldr r3,=rawBios
+//	ldr r3,=rawBios
 //	str r3,g_BIOSBASE_US
 //	str r3,g_BIOSBASE_JP
 //	str r3,g_BIOSBASE_COLECO
@@ -318,8 +318,9 @@ tbLoop1:
 	ldreq r1,g_BIOSBASE_GG		;@ GG
 	bicne r2,r2,#0x40			;@ X as Start/Pause only on HW_GG
 	bicne r0,r0,#GG_MODE
+	cmpne r9,#HW_SMS2
 	cmpne r9,#HW_MEGADRIVE
-	biceq r2,r2,#0x20			;@ Reset unavailable on HW_GG & HW_MD (& HW_SMS2)
+	biceq r2,r2,#0x20			;@ Reset unavailable on HW_GG, HW_SMS2 & HW_MEGADRIVE
 	str r0,g_emuFlags
 	strb r2,g_config
 	cmp r1,#0
diff --git a/source/Gfx.s b/source/Gfx.s
index c9e00b6..28991f0 100644
--- a/source/Gfx.s
+++ b/source/Gfx.s
@@ -163,7 +163,8 @@ ppi:
 	adds r1,r1,#1
 	bne ppi
 
-	bl gfxReset
+	bl setupScaling
+	bl VDP0ApplyScaling
 	ldmfd sp!,{lr}
 	bx lr
 ;@----------------------------------------------------------------------------
diff --git a/source/Gui.c b/source/Gui.c
index e5fac17..a2cc7a5 100644
--- a/source/Gui.c
+++ b/source/Gui.c
@@ -29,7 +29,7 @@
 #include "AY38910/Version.h"
 #include "SCC/Version.h"
 
-#define EMUVERSION "V1.1.2 2021-10-11"
+#define EMUVERSION "V1.1.3 2021-10-12"
 
 extern u8 sordM5Input;		// SordM5.s
 
@@ -82,6 +82,7 @@ static void glassesSet(void);
 static void countrySet(void);
 static void machineSet(void);
 static void biosSet(void);
+static void ym2413Set(void);
 
 static void dip0Set0_1(void);
 static void dip0Set1_1(void);
@@ -149,7 +150,7 @@ static const fptr fnList2[] = {ui4, ui5, ui6, ui7, ui9};
 static const fptr fnList3[] = {uiDummy};
 static const fptr fnList4[] = {autoBSet, autoASet, controllerSet, swapABSet, joypadSet, selectSet, rffSet};
 static const fptr fnList5[] = {scalingSet, flickSet, brightSet, colorSet, borderSet, spriteSet, glassesSet, bgrLayerSet, sprLayerSet};
-static const fptr fnList6[] = {countrySet, machineSet, ui8};
+static const fptr fnList6[] = {countrySet, machineSet, ui8, ym2413Set};
 static const fptr fnList7[] = {speedSet, autoStateSet, autoSettingsSet, autoNVRAMSet, autoPauseGameSet, powerSaveSet, screenSwapSet, debugTextSet, sleepSet};
 static const fptr fnList8[] = {biosSet, selectUSBios, selectJPBios, selectGGBios, selectCOLECOBios, selectMSXBios, selectSORDM5Bios};
 static const fptr fnList9[] = {uiDummy};
@@ -401,6 +402,7 @@ static void uiMachine() {
 	drawSubItem("Region: ",cntrTxt[g_region]);
 	drawSubItem("Machine: ",machTxt[g_machineSet]);
 	drawMenuItem(" Bios Settings ->");
+	drawSubItem("YM2413: ",biosTxt[ym2413Enabled&1]);
 }
 
 static void uiSettings() {
@@ -1505,6 +1507,10 @@ void glassesSet() {
 }
 
 
+void biosSet() {
+	g_configSet ^= 0x80;
+}
+
 void countrySet() {
 	int i;
 	g_region = (g_region+1)&3;
@@ -1530,8 +1536,8 @@ void machineSet() {
 	}
 }
 
-void biosSet() {
-	g_configSet ^= 0x80;
+void ym2413Set() {
+	ym2413Enabled ^= 0x01;
 }
 
 
diff --git a/source/Memory.s b/source/Memory.s
index 8486751..615b559 100644
--- a/source/Memory.s
+++ b/source/Memory.s
@@ -145,8 +145,8 @@ ram1S_W:					;@ Write ram ($E000-$FFFF), mirror. Bankswitch
 	bhi BankSwitch2_W			;@ $FFFF
 	beq BankSwitch1_W			;@ $FFFE
 	bmi BankSwitch0_W			;@ $FFFD
-;	mov r11,r11
-;	bx lr
+	mov r11,r11
+	bx lr
 ;@----------------------------------------------------------------------------
 LCDGlasses:
 ;@----------------------------------------------------------------------------
@@ -154,7 +154,7 @@ LCDGlasses:
 	ldrb r1,[r1]
 	cmp r1,#HW_MARK3
 	cmpne r1,#HW_SMS1
-	cmpne r1,#HW_SMS2
+	cmpne r1,#HW_MEGADRIVE
 	bxne lr
 	ldr r1,=g_3DEnable
 	ldrb r1,[r1]
diff --git a/source/io.h b/source/io.h
index 63aec01..b9888e5 100644
--- a/source/io.h
+++ b/source/io.h
@@ -10,6 +10,7 @@ extern u8 colecoKey;
 extern u8 sc3Keyboard;
 extern u8 keyboardRows[8];
 extern u8 inputHW;
+extern u8 ym2413Enabled;
 extern int coinCounter0;
 extern int coinCounter1;
 extern u8 dipSwitch0;
diff --git a/source/io.s b/source/io.s
index 3194027..19a93e0 100644
--- a/source/io.s
+++ b/source/io.s
@@ -10,6 +10,7 @@
 	.global Z80Out
 	.global joyCfg
 	.global inputHW
+	.global ym2413Enabled
 	.global joy0State
 	.global joy1State
 	.global acExtra
@@ -58,7 +59,7 @@ IO_Params_SG1000_R:
 	.long 0x00410063, PPI1PortBR		;@ 0x41-0x5D, 0xC1-0xDD
 	.long 0x00420063, PPI1PortCR		;@ 0x42-0x5E, 0xC2-0xDE
 	.long 0x00430063, PPI1PortDR		;@ 0x43-0x5F, 0xC3-0xDF
-	.long 0x00000000, empty_R_SMS1		;@ 0x00-0x9F, 0xE0-0xFF
+	.long 0x00000000, empty_R_SMS1		;@ 0x00-0x1F, 0x60-0x9F, 0xE0-0xFF
 IO_Params_SG1000_W:
 	.long 0x006000E0, SN76496_W			;@ 0x60-0x7F
 	.long 0x00A000E1, VDP0DataTMSW		;@ 0xA0-0xBE
@@ -81,7 +82,7 @@ IO_Params_OMV_R:
 	.long 0x00E100E7, OMVPort2_R		;@ 0xE1-0xF9
 	.long 0x00E200E7, OMVPort3_R		;@ 0xE2-0xFA
 	.long 0x00E300E7, OMVPort4_R		;@ 0xE3-0xFB
-	.long 0x00000000, empty_R_SMS1		;@ 0x00-0x9F, 0xE0-0xFF
+	.long 0x00000000, empty_R_SMS1		;@ 0x00-0x1F, 0x40-0x9F, 0xFC-0xFF
 IO_Params_OMV_W:
 	.long 0x006000E0, SN76496_W			;@ 0x60-0x7F
 	.long 0x00A000E1, VDP0DataTMSW		;@ 0xA0-0xBE
@@ -96,17 +97,17 @@ IO_Params_Mark3_R:
 	.long 0x004100C1, VDP0HCounterR		;@ 0x41-0x7F
 	.long 0x008000C1, VDP0DataR			;@ 0x80-0xBE
 	.long 0x008100C1, VDP0StatR			;@ 0x81-0xBF
+	.long 0x00F000FC, ExternalIO_R		;@ 0xF0-0xF2
 	.long 0x00C000C1, ExtIO_0_SMS_R		;@ 0xC0-0xFE
 	.long 0x00C100C1, ExtIO_1_SMS_R		;@ 0xC1-0xFF
 	.long 0x00000000, empty_R_SMS1		;@ 0x00-0x3F
 IO_Params_Mark3_W:
-//	.long 0x000000C1, MemCtrl_SMS_W		;@ 0x00-0x3E
 	.long 0x004000C0, SN76496_W			;@ 0x40-0x7F
 	.long 0x008000C1, VDP0DataSMSW		;@ 0x80-0xBE
 	.long 0x008100C1, VDP0CtrlW			;@ 0x81-0xBF
 	.long 0x00FD00FF, SDSC_Debug_W		;@ 0xFD
 	.long 0x00C000C0, ExternalIO_W		;@ 0xC0-0xFF
-	.long 0x00000000, empty_W			;@ 0x01-0x3F
+	.long 0x00000000, empty_W			;@ 0x00-0x3F
 
 ;@----------------------------------------------------------------------------
 ;@ SMS1
@@ -608,7 +609,8 @@ joy1Extra:		.byte 0
 joyMode:		.byte 0
 colecoKey:		.byte 0
 inputHW:		.byte 0
-				.byte 0
+ym2413Enabled:	.byte 1
+
 sc3Keyboard:
 keyboardRows:
 keyboardRow0:	.byte 0xFF
@@ -917,13 +919,12 @@ StereoCtrl_GG_W:			;@ GG stereo control, 0x06
 ;@------------------------------------------------------------------------------
 IOCtrl_GG_W:				;@ GG com port stuff, 0x00-0x07
 ;@------------------------------------------------------------------------------
-	adr r1,GGIO
-	strb r0,[r1,addy]
+	strb r0,[pc,addy]
 	bx lr
-GGIO_Default:
-	.byte 0xC0,0x7F,0xFF,0x00,0xFF,0x00,0xFF,0xFF
 GGIO:
 	.byte 0xC0,0x7F,0xFF,0x00,0xFF,0x00,0xFF,0xFF
+GGIO_Default:
+	.byte 0xC0,0x7F,0xFF,0x00,0xFF,0x00,0xFF,0xFF
 ;@------------------------------------------------------------------------------
 IOCtrl_SMS_W:
 ;@------------------------------------------------------------------------------
@@ -963,6 +964,9 @@ IOCtrl_SMS_W:
 ;@----------------------------------------------------------------------------
 ExternalIO_R:
 ;@----------------------------------------------------------------------------
+	ldrb r1,ym2413Enabled
+	cmp r1,#0
+	ldreq pc,emptyReadPtr
 	cmp addy,#0xF1				;@ FM Unit
 	beq YM2413_0_StatusR
 	cmp addy,#0xF2				;@ FM/PSG enable/disable?
@@ -971,6 +975,9 @@ ExternalIO_R:
 ;@----------------------------------------------------------------------------
 ExternalIO_W:
 ;@----------------------------------------------------------------------------
+	ldrb r1,ym2413Enabled
+	cmp r1,#0
+	beq empty_W
 	cmp addy,#0xF0				;@ FM Unit
 	beq YM2413_0_AddressW
 	cmp addy,#0xF1				;@ FM Unit