diff --git a/Cart_Reader/N64.ino b/Cart_Reader/N64.ino
index 91169277..ff35504c 100644
--- a/Cart_Reader/N64.ino
+++ b/Cart_Reader/N64.ino
@@ -4050,7 +4050,9 @@ unsigned long verifyFlashrom_N64() {
    N64 Gameshark Flash Functions
  *****************************************/
 void flashGameshark_N64() {
+  int flashSize = 0;
   // Check flashrom ID's
+  unlockGSAddressRanges();
   idGameshark_N64();
 
   // Check for SST 29LE010 (0808)/SST 28LF040 (0404)/AMTEL AT29LV010A (3535)/SST 29EE010 (0707)
@@ -4078,7 +4080,6 @@ void flashGameshark_N64() {
     filePath[0] = '\0';
     sd.chdir("/");
     fileBrowser(F("Select z64 file"));
-    display_Clear();
     display_Update();
 
     // Create filepath
@@ -4088,18 +4089,25 @@ void flashGameshark_N64() {
     if (myFile.open(filePath, O_READ)) {
       // Get rom size from file
       fileSize = myFile.fileSize();
+      display_Clear();
       print_Msg(F("File size: "));
       print_Msg(fileSize / 1024);
-      println_Msg(F("KB"));
+      println_Msg(F(" KB"));
       display_Update();
 
-      // Compare file size to flashrom size
-      if (fileSize > 262144) {
+      // Compare file size to flashrom size for 1 Mbit eeproms
+      if (fileSize > 262144 && (flashid == 0x0808 || flashid == 0x3535 || flashid == 0x0707)) {
+        print_FatalError(file_too_big_STR);
+      }
+
+      // Compare file size to flashrom size for 1 Mbit eeproms
+      if (fileSize > 1048576 && flashid == 0x0404) {
         print_FatalError(file_too_big_STR);
       }
 
       // SST 29LE010, chip erase not needed as this eeprom automaticly erases during the write cycle
       eraseGameshark_N64();
+      blankCheck_N64();
 
       // Write flashrom
       print_Msg(F("Writing "));
@@ -4116,14 +4124,19 @@ void flashGameshark_N64() {
       writeErrors = verifyGameshark_N64();
 
       if (writeErrors == 0) {
-        println_Msg(F("OK"));
+        display_Clear();
+        display_Update();
+        println_Msg(F("Verfied OK"));
         println_Msg(F(""));
         println_Msg(F("Turn Cart Reader off now"));
         display_Update();
         while (1)
           ;
       } else {
-        print_Msg(writeErrors);
+        display_Clear();
+        display_Update();
+        println_Msg(F("Verification Failed"));
+        println_Msg(writeErrors);
         print_Msg(F(" bytes "));
         print_Error(did_not_verify_STR);
       }
@@ -4131,12 +4144,6 @@ void flashGameshark_N64() {
       print_Error(F("Can't open file"));
     }
   }
-  // If the ID is unknown show error message
-  else {
-    print_Msg(F("ID: "));
-    println_Msg(flashid_str);
-    print_Error(F("Unknown flashrom"));
-  }
 
   // Prints string out of the common strings array either with or without newline
   print_STR(press_button_STR, 1);
@@ -4146,37 +4153,72 @@ void flashGameshark_N64() {
   display_Update();
 }
 
+void unlockGSAddressRanges() {
+    // This enables using the 0x1EEx_xxxx, 0x1EFx_xxxx, and 0x1ECx_xxxx address ranges, necessary for writing to all supported chips
+    setAddress_N64(0x10400400);
+    writeWord_N64(0x1E);
+    writeWord_N64(0x1E);
+}
 
 //Test for SST 29LE010  or SST 28LF040 (0404) or AMTEL AT29LV010A (3535) or SST 29EE010 (0707)
 void idGameshark_N64() {
+  flashid = 0x0;
   //Send flashrom ID command
-  setAddress_N64(romBase + 0xAAAA);
+  setAddress_N64(0x1EF0AAA8);
   writeWord_N64(0xAAAA);
-  setAddress_N64(romBase + 0x5554);
+  setAddress_N64(0x1EE05554);
   writeWord_N64(0x5555);
-  setAddress_N64(romBase + 0xAAAA);
+  setAddress_N64(0x1EF0AAA8);
   writeWord_N64(0x9090);
 
-  setAddress_N64(romBase);
+  setAddress_N64(0x1EC00000);
   // Read 1 byte vendor ID
   readWord_N64();
   // Read 2 bytes flashrom ID
   flashid = readWord_N64();
+
+  if (flashid == 0x0808 || flashid == 0x3535 || flashid == 0x0707) {
+    flashSize = 262144;
+  }
+
+  if (flashid == 0x0404) {
+    //Set SST 28LF040 flashrom size
+    flashSize = 1048574;
+      if (flashid != 0x0404) {
+        println_Msg(F("Check cart connection"));
+        println_Msg(F("Unknown Flash ID"));
+        sprintf(flashid_str, "%04X", flashid);
+        print_STR(press_button_STR, 1);
+        display_Update();
+        wait();
+        mainMenu();
+      }
+  }
   sprintf(flashid_str, "%04X", flashid);
   // Reset flashrom
   resetGameshark_N64();
 }
 
-//Reset ST29LE010
 void resetGameshark_N64() {
-  // Send reset Command
-  setAddress_N64(romBase + 0xAAAA);
-  writeWord_N64(0xAAAA);
-  setAddress_N64(romBase + 0x5554);
-  writeWord_N64(0x5555);
-  setAddress_N64(romBase + 0xAAAA);
-  writeWord_N64(0xF0F0);
-  delay(100);
+  if (flashid == 0x0808 || flashid == 0x3535 || flashid == 0x0707) {
+    // Send reset command for SST 29LE010 / AMTEL AT29LV010A / SST 29EE010
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0xAAAA);
+    setAddress_N64(0x1EE05554);
+    writeWord_N64(0x5555);
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0xF0F0);
+    delay(100);
+  } else if (flashid == 0x0404) {
+    // Send reset command for SST 28LF040
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0xAAAA);
+    setAddress_N64(0x1EE05554);
+    writeWord_N64(0x5555);
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0xFFFF);
+    delay(300);
+  }
 }
 
 // Read rom and save to the SD card
@@ -4203,7 +4245,7 @@ void backupGameshark_N64() {
     print_FatalError(sd_error_STR);
   }
 
-  for (unsigned long currByte = romBase + 0xC00000; currByte < (romBase + 0xC00000 + 262144); currByte += 512) {
+  for (unsigned long currByte = romBase + 0xEC00000; currByte < (romBase + 0xEC00000 + flashSize); currByte += 512) {
     // Blink led
     if (currByte % 16384 == 0)
       blinkLED();
@@ -4227,55 +4269,169 @@ void backupGameshark_N64() {
   myFile.close();
 }
 
-// Send chip erase to the two SST29LE010 inside the Gameshark
 void eraseGameshark_N64() {
   println_Msg(F("Erasing..."));
   display_Update();
 
-  //Sending erase command according to datasheet
-  setAddress_N64(romBase + 0xAAAA);
-  writeWord_N64(0xAAAA);
-  setAddress_N64(romBase + 0x5554);
-  writeWord_N64(0x5555);
-  setAddress_N64(romBase + 0xAAAA);
-  writeWord_N64(0x8080);
-  setAddress_N64(romBase + 0xAAAA);
-  writeWord_N64(0xAAAA);
-  setAddress_N64(romBase + 0x5554);
-  writeWord_N64(0x5555);
-  setAddress_N64(romBase + 0xAAAA);
-  writeWord_N64(0x1010);
+  // Send chip erase to SST 29LE010 / AMTEL AT29LV010A / SST 29EE010
+  if (flashid == 0x0808 || flashid == 0x3535 || flashid == 0x0707) {
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0xAAAA);
+    setAddress_N64(0x1EE05554);
+    writeWord_N64(0x5555);
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0x8080);
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0xAAAA);
+    setAddress_N64(0x1EE05554);
+    writeWord_N64(0x5555);
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0x1010);
 
-  delay(20);
-}
+    delay(20);
+  }
 
-// Write Gameshark with 2x SST29LE010 Eeproms
-void writeGameshark_N64() {
-  // Each 29LE010 has 1024 pages, each 128 bytes in size
-  for (unsigned long currPage = 0; currPage < fileSize / 2; currPage += 128) {
-    // Fill SD buffer with twice the amount since we flash 2 chips
-    myFile.read(sdBuffer, 256);
-    // Blink led
-    blinkLED();
+  if (flashid == 0x0404) {
+    //Unprotect flash
+    setAddress_N64(0x1EF03044);
+    readWord_N64();
+    setAddress_N64(0x1EE03040);
+    readWord_N64();
+    setAddress_N64(0x1EE03044);
+    readWord_N64();
+    setAddress_N64(0x1EE00830);
+    readWord_N64();
+    setAddress_N64(0x1EF00834);
+    readWord_N64();
+    setAddress_N64(0x1EF00830);
+    readWord_N64();
+    setAddress_N64(0x1EE00834);
+    readWord_N64();
+    delay(1000);
 
-    //Send page write command to both flashroms
-    setAddress_N64(romBase + 0xAAAA);
+    //Erase flash
+    setAddress_N64(0x1EF0AAA8);
     writeWord_N64(0xAAAA);
-    setAddress_N64(romBase + 0x5554);
+    setAddress_N64(0x1EE05554);
     writeWord_N64(0x5555);
-    setAddress_N64(romBase + 0xAAAA);
-    writeWord_N64(0xA0A0);
-
-    // Write 1 page each, one flashrom gets the low byte, the other the high byte.
-    for (unsigned long currByte = 0; currByte < 256; currByte += 2) {
-      // Set address
-      setAddress_N64(romBase + 0xC00000 + (currPage * 2) + currByte);
-      // Join two bytes into one word
-      word currWord = ((sdBuffer[currByte] & 0xFF) << 8) | (sdBuffer[currByte + 1] & 0xFF);
-      // Send byte data
-      writeWord_N64(currWord);
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0x3030);
+    setAddress_N64(0x1EF0AAA8);
+    writeWord_N64(0x3030);
+    delay(1000);
+  }
+}
+
+void blankCheck_N64() {
+    // Blankcheck
+    println_Msg(F("Blankcheck..."));
+    display_Update();
+
+    for (unsigned long currSector = 0; currSector < flashSize; currSector += 131072) {
+      // Blink led
+      blinkLED();
+      for (unsigned long currSdBuffer = 0; currSdBuffer < 131072; currSdBuffer += 512) {
+        for (int currByte = 0; currByte < 512; currByte += 2) {
+          // Read flash
+          setAddress_N64(romBase + 0xEC00000 + currSector + currSdBuffer + currByte);
+          // Compare both
+          if (readWord_N64() != 0xFFFF) {
+            println_Msg(F("Not empty"));
+            print_FatalError(F("Erase failed"));
+          }
+        }
+      }
+    }
+}
+
+void writeGameshark_N64() {
+  // Write Gameshark with 2x SST 29LE010 / AMTEL AT29LV010A / SST 29EE010 Eeproms
+  if (flashid == 0x0808 || flashid == 0x3535 || flashid == 0x0707) {
+    // Each 29LE010 has 1024 pages, each 128 bytes in size
+    myFile.seek(0);
+    for (unsigned long currPage = 0; currPage < fileSize / 2; currPage += 128) {
+      // Fill SD buffer with twice the amount since we flash 2 chips
+      myFile.read(sdBuffer, 256);
+      // Blink led
+      blinkLED();
+
+      //Send page write command to both flashroms
+      setAddress_N64(0x1EF0AAA8);
+      writeWord_N64(0xAAAA);
+      setAddress_N64(0x1EE05554);
+      writeWord_N64(0x5555);
+      setAddress_N64(0x1EF0AAA8);
+      writeWord_N64(0xA0A0);
+
+      // Write 1 page each, one flashrom gets the low byte, the other the high byte.
+      for (unsigned long currByte = 0; currByte < 256; currByte += 2) {
+        // Set address
+        setAddress_N64(romBase + 0xEC00000 + (currPage * 2) + currByte);
+        // Join two bytes into one word
+        word currWord = ((sdBuffer[currByte] & 0xFF) << 8) | (sdBuffer[currByte + 1] & 0xFF);
+        // Send byte data
+        writeWord_N64(currWord);
+      }
+      delay(30);
+    }
+  }
+
+  if (flashid == 0x0404) {
+    // Write Gameshark with 2x SST 28LF040
+    //Initialize progress bar
+    uint32_t processedProgressBar = 0;
+    uint32_t totalProgressBar = (uint32_t)(fileSize);
+    draw_progressbar(0, totalProgressBar);
+    bool toggle = true;
+    myFile.seek(0);
+    for (unsigned long currSector = 0; currSector < fileSize; currSector += 16384) {
+      // Blink led
+      blinkLED();
+      for (unsigned long currSdBuffer = 0; currSdBuffer < 16384; currSdBuffer += 256) {
+        // Fill SD buffer
+        myFile.read(sdBuffer, 256);
+        for (unsigned long currByte = 0; currByte < 256; currByte += 2) {
+
+          // Send byte program command
+          setAddress_N64(0x1EF0AAA8);
+          writeWord_N64(0xAAAA);
+          setAddress_N64(0x1EE05554);
+          writeWord_N64(0x5555);
+          setAddress_N64(0x1EF0AAA8);
+          writeWord_N64(0x1010);
+
+          // Set address
+          setAddress_N64(romBase + 0xEC00000 + currSector + currSdBuffer + currByte);
+          
+          // Join two bytes into one word
+          word currWord = ((sdBuffer[currByte] & 0xFF) << 8) | (sdBuffer[currByte + 1] & 0xFF);
+          
+          // Send byte data
+          writeWord_N64(currWord);
+          delayMicroseconds(60);
+        }
+      processedProgressBar += 256;
+      draw_progressbar(processedProgressBar, totalProgressBar);
+      blinkLED();
+      }
     }
-    delay(30);
+
+    //Protect flash
+    setAddress_N64(0x1EF03044);
+    readWord_N64();
+    setAddress_N64(0x1EE03040);
+    readWord_N64();
+    setAddress_N64(0x1EE03044);
+    readWord_N64();
+    setAddress_N64(0x1EE00830);
+    readWord_N64();
+    setAddress_N64(0x1EF00834);
+    readWord_N64();
+    setAddress_N64(0x1EF00830);
+    readWord_N64();
+    setAddress_N64(0x1EE00814);
+    readWord_N64();
+    delay(1000);
   }
 }
 
@@ -4294,14 +4450,10 @@ unsigned long verifyGameshark_N64() {
           // Join two bytes into one word
           word currWord = ((sdBuffer[currByte] & 0xFF) << 8) | (sdBuffer[currByte + 1] & 0xFF);
           // Read flash
-          setAddress_N64(romBase + 0xC00000 + currSector + currSdBuffer + currByte);
+          setAddress_N64(romBase + 0xEC00000 + currSector + currSdBuffer + currByte);
           // Compare both
           if (readWord_N64() != currWord) {
-            if ((flashid == 0x0808) && (currSector + currSdBuffer + currByte > 0x3F) && (currSector + currSdBuffer + currByte < 0x1080)) {
-              // Gameshark maps this area to the bootcode of the plugged in cartridge
-            } else {
-              writeErrors++;
-            }
+            writeErrors++;
           }
         }
       }