diff --git a/src/DiskImage.cpp b/src/DiskImage.cpp
index 5eb4251..171075f 100644
--- a/src/DiskImage.cpp
+++ b/src/DiskImage.cpp
@@ -30,6 +30,8 @@ extern "C"
 #include "rpi-gpio.h"
 }
 
+extern u32 HashBuffer(const void* pBuffer, u32 length);
+
 unsigned char DiskImage::readBuffer[READBUFFER_SIZE];
 
 static unsigned char compressionBuffer[HALF_TRACK_COUNT * MAX_TRACK_LENGTH];
@@ -144,6 +146,7 @@ void DiskImage::Close()
 	memset(trackLengths, 0, sizeof(trackLengths));
 	diskType = NONE;
 	fileInfo = 0;
+	hash = 0;
 }
 
 void DiskImage::DumpTrack(unsigned track)
@@ -762,7 +765,9 @@ bool DiskImage::OpenG64(const FILINFO* fileInfo, unsigned char* diskImage, unsig
 
 	if (memcmp(diskImage, "GCR-1541", 8) == 0)
 	{
-		//DEBUG_LOG("Is G64\r\n");
+		hash = HashBuffer(diskImage, size);
+
+		//DEBUG_LOG("Is G64 %08x\r\n", hash);
 
 		unsigned char numTracks = diskImage[9];
 		//DEBUG_LOG("numTracks = %d\r\n", numTracks);
diff --git a/src/DiskImage.h b/src/DiskImage.h
index a135c16..42a2a7a 100644
--- a/src/DiskImage.h
+++ b/src/DiskImage.h
@@ -167,6 +167,8 @@ public:
 	bool WriteD64(char* name = 0);
 	bool WriteG64(char* name = 0);
 
+	unsigned GetHash() const { return hash; }
+
 private:
 	void CloseD64();
 	void CloseG64();
@@ -204,6 +206,7 @@ private:
 	unsigned attachedImageSize;
 	DiskType diskType;
 	const FILINFO* fileInfo;
+	unsigned hash;
 
 	unsigned short trackLengths[HALF_TRACK_COUNT];
 	union
diff --git a/src/main.cpp b/src/main.cpp
index 9433eb6..7585397 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -580,6 +580,24 @@ static bool Snoop(u8 a)
 	return false;
 }
 
+//--------------------------------------------------------------------------------------
+// This is an implementation of FNV-1a
+// (http://www.isthe.com/chongo/tech/comp/fnv/)
+//--------------------------------------------------------------------------------------
+u32 HashBuffer(const void* pBuffer, u32 length)
+{
+	u8*	pu8Buffer = (u8*)pBuffer;
+	u32	hash = 0x811c9dc5U;
+
+	while (length)
+	{
+		hash ^= *pu8Buffer++;
+		hash *= 16777619U;
+		--length;
+	}
+	return hash;
+}
+
 EmulatingMode BeginEmulating(FileBrowser* fileBrowser, const char* filenameForIcon)
 {
 	DiskImage* diskImage = diskCaddy.SelectFirstImage();
@@ -679,7 +697,7 @@ EXIT_TYPE Emulate1541(FileBrowser* fileBrowser)
 	const int headSoundFreq = 1000000 / options.SoundOnGPIOFreq();	// 1200Hz = 1/1200 * 10^6;
 	unsigned char oldHeadDir;
 	int resetCount = 0;
-
+	bool refreshOutsAfterCPUStep = true;
 	unsigned numberOfImages = diskCaddy.GetNumberOfImages();
 	unsigned numberOfImagesMax = numberOfImages;
 	if (numberOfImagesMax > 10)
@@ -707,6 +725,14 @@ EXIT_TYPE Emulate1541(FileBrowser* fileBrowser)
 	//resetWhileEmulating = false;
 	selectedViaIECCommands = false;
 
+	u32 hash = pi1541.drive.GetDiskImage()->GetHash();
+	// 0x42c02586 = maniac_mansion_s1[lucasfilm_1989](ntsc).g64
+	// 0x18651422 = aliens[electric_dreams_1987].g64
+	if (hash == 0x42c02586 || hash == 0x18651422)
+	{
+		refreshOutsAfterCPUStep = false;
+	}
+
 	while (exitReason == EXIT_UNKNOWN)
 	{
 
@@ -738,7 +764,9 @@ EXIT_TYPE Emulate1541(FileBrowser* fileBrowser)
 			//read32(ARM_SYSTIMER_CLO);
 			//read32(ARM_SYSTIMER_CLO);
 
-			IEC_Bus::RefreshOuts1541();	// Now output all outputs.
+//			IEC_Bus::ReadEmulationMode1541();
+			if (refreshOutsAfterCPUStep)
+				IEC_Bus::RefreshOuts1541();	// Now output all outputs.
 
 			IEC_Bus::OutputLED = pi1541.drive.IsLEDOn();
 			if (IEC_Bus::OutputLED ^ oldLED)