diff --git a/arm11/source/hw/mcu.c b/arm11/source/hw/mcu.c
index 2e8b178..3c5a291 100755
--- a/arm11/source/hw/mcu.c
+++ b/arm11/source/hw/mcu.c
@@ -172,14 +172,14 @@ void MCU_HandleInterrupts(u32 __attribute__((unused)) irqn)
 			case MCU_SHELL_OPEN:
 				MCU_PushToLCD(true);
 				MCU_UpdateShellState(true);
-				TIMER_WaitTicks(CLK_MS_TO_TICKS(10));
+				TIMER_WaitTicks(CLK_MS_TO_TICKS(5));
 				MCU_ResetLED();
 				break;
 
 			case MCU_SHELL_CLOSE:
 				MCU_PushToLCD(false);
 				MCU_UpdateShellState(false);
-				TIMER_WaitTicks(CLK_MS_TO_TICKS(10));
+				TIMER_WaitTicks(CLK_MS_TO_TICKS(5));
 				break;
 
 			case MCU_VOL_SLIDER:
@@ -196,7 +196,7 @@ void MCU_HandleInterrupts(u32 __attribute__((unused)) irqn)
 
 void MCU_Init(void)
 {
-	u32 mask = 0xFFBF0800;
+	const u32 mask = 0xFFBF0800;
 	MCU_WriteRegBuf(REG_INT_EN, (const u8*)&mask, sizeof(mask));
 	MCU_ResetLED();
 
diff --git a/arm11/source/hw/spi.c b/arm11/source/hw/spi.c
index a5bbc39..358f546 100755
--- a/arm11/source/hw/spi.c
+++ b/arm11/source/hw/spi.c
@@ -126,3 +126,10 @@ void SPI_Init(void)
 	// interface used during the NDS days
 	*REG_CFG_SPI_CNT = 7;
 }
+
+void SPI_Deinit(void)
+{
+	// Keep backwards compatibility with software that
+	// assumes all bus interfaces will be set to old
+	*REG_CFG_SPI_CNT = 0;
+}
diff --git a/arm11/source/hw/spi.h b/arm11/source/hw/spi.h
index 6b3a24b..bea9251 100755
--- a/arm11/source/hw/spi.h
+++ b/arm11/source/hw/spi.h
@@ -29,3 +29,4 @@ typedef struct {
 int SPI_DoXfer(u32 dev, const SPI_XferInfo *xfer, u32 xfer_cnt);
 
 void SPI_Init(void);
+void SPI_Deinit(void);
diff --git a/arm11/source/system/sys.c b/arm11/source/system/sys.c
index c8a2a50..a607421 100755
--- a/arm11/source/system/sys.c
+++ b/arm11/source/system/sys.c
@@ -118,7 +118,7 @@ void SYS_CoreZeroInit(void)
 	GPU_SetFramebufferMode(1, PDC_RGB24);
 
 	MCU_PushToLCD(true);
-	TIMER_WaitTicks(CLK_MS_TO_TICKS(10));
+	TIMER_WaitTicks(CLK_MS_TO_TICKS(5));
 }
 
 void SYS_CoreInit(void)
@@ -163,6 +163,8 @@ void __attribute__((noreturn)) SYS_CoreShutdown(void)
 	ARM_SetACR(ARM_GetACR() &
 		~(ACR_RETSTK | ACR_DBPRED | ACR_SBPRED | ACR_FOLDING | ACR_SMP));
 
+	SPI_Deinit();
+
 	if (!core) {
 		while(*LEGACY_BOOT_ENTRYPOINT == 0);
 		((void (*)(void))(*LEGACY_BOOT_ENTRYPOINT))();
diff --git a/common/pxi.h b/common/pxi.h
index 7012076..1bb5ee0 100644
--- a/common/pxi.h
+++ b/common/pxi.h
@@ -68,6 +68,7 @@ enum {
 #define PXI_CNT_RECV_FIFO_EMPTY       (BIT(8))
 #define PXI_CNT_RECV_FIFO_FULL        (BIT(9))
 #define PXI_CNT_RECV_FIFO_AVAIL_IRQ   (BIT(10))
+#define PXI_CNT_ACKNOWLEDGE_ERROR     (BIT(14))
 #define PXI_CNT_ENABLE_FIFO           (BIT(15))
 
 static inline void PXI_SetRemote(u8 msg)
@@ -93,7 +94,8 @@ static inline void PXI_Reset(void)
 		*PXI_RECV;
 
 	*PXI_CNT = 0;
-	*PXI_CNT = PXI_CNT_RECV_FIFO_AVAIL_IRQ | PXI_CNT_ENABLE_FIFO;
+	*PXI_CNT = PXI_CNT_RECV_FIFO_AVAIL_IRQ | PXI_CNT_ENABLE_FIFO |
+				PXI_CNT_ACKNOWLEDGE_ERROR;
 
 	PXI_SetRemote(0xFF);
 }