diff --git a/source/arm9/firmwriter.c b/source/arm9/firmwriter.c
index d34f053..dcb4be8 100644
--- a/source/arm9/firmwriter.c
+++ b/source/arm9/firmwriter.c
@@ -11,17 +11,94 @@
 #include "arm9/menu.h"
 #include "arm9/timer.h"
 
-void firmwriterInit()
-{
+static size_t totalToWrite;
+static size_t totalWritten;
+static size_t curSector;
+static bool protectSig;
+static bool failure;
 
+void firmwriterInit(size_t sector, size_t sectorCount, bool preserveSignature)
+{
+	if(sectorCount < 2)
+		panic();
+
+	totalToWrite = sectorCount;
+	totalWritten = 0;
+	// +1 because we'll write the firm header afterwards
+	curSector = sector + 1;
+	protectSig = preserveSignature;
+	failure = false;
 }
 
 bool firmwriterWriteBlock()
 {
+	void *sourceBuf = (void *) FIRM_LOAD_ADDR + (totalWritten + 1) * 0x200;
+	u32 blockData[0x80];
 
+	if(totalWritten >= totalToWrite - 1)
+		return false;
+
+	if(!dev_rawnand->write_sector(curSector, 0x200, sourceBuf))
+	{
+		failure = true;
+		return false;
+	}
+
+	/* read back data and compare */
+	if(!dev_rawnand->read_sector(sector, sizeof blockData, blockData) ||
+		memcmp(sourceBuf, blockData, sizeof blockData) != 0)
+	{
+		failure = true;
+		return false;
+	}
+
+	curSector++;
+	totalWritten++;
+
+	return true;
+}
+
+bool firmwriterIsDone()
+{
+     if(failure)
+		return false;
+
+	 return totalWritten == totalToWrite - 1;
 }
 
 bool firmwriterFinish()
 {
+	u32 blockData[0x80];
+	firm_header header;
+	void *firmBuf = (void *) FIRM_LOAD_ADDR;
+	size_t sector = curSector - totalWritten - 1;
 
+	/* read signature from NAND if we want to keep sighax */
+	if(protectSig)
+	{
+		if(!dev_rawnand->read_sector(sector, sizeof header, &header))
+		{
+			failure = true;
+			return false;
+		}
+
+		memcpy(header, firmBuf, 0x100);
+		firmBuf = (void *) header;
+	}
+
+	if(!dev_rawnand->write_sector(sector, 0x200, firmBuf);
+	{
+		failure = true;
+		return false;
+	}
+
+	/* read back data and compare */
+	if(!dev_rawnand->read_sector(sector, sizeof blockData, blockData) ||
+		memcmp(firmBuf, blockData, sizeof blockData) != 0)
+	{
+		failure = true;
+		return false;
+	}
+
+	return true;
 }
diff --git a/source/arm9/menu_update.c b/source/arm9/menu_update.c
index 88a4c70..cc5848d 100644
--- a/source/arm9/menu_update.c
+++ b/source/arm9/menu_update.c
@@ -13,12 +13,17 @@
 #include "arm9/menu.h"
 #include "arm9/timer.h"
 
+#define MIN_UPDATE_SIZE	0x1000
+
 static const char *updateFilePath = "sdmc:\\fastboot3ds.bin";
+static const char *installPath = "firm0"
 
 bool menuUpdateLoader()
 {
 	u8 *updateBuffer = (u8 *) FIRM_LOAD_ADDR;
 	FILINFO fileStat;
+	size_t fwSize;
+	size_t sector;
 
 	uiClearConsoles();
 	consoleSelect(&con_top);
@@ -39,6 +44,15 @@
 		uiPrintError("Invalid update file!\n");
 		goto fail;
 	}
+
+	// XXX
+	fwSize = calcFirmwareSize();
+
+	if(fwSize < MIN_UPDATE_SIZE || fwSize % 0x200)	// this would be really odd.
+	{
+		uiPrintError("Invalid update file!\n");
+		goto fail;
+	}
 	
 	// verify fastboot magic
 	if(memcmp(updateBuffer+0x208, "FASTBOOT 3DS   ", 0x10) != 0)
@@ -67,8 +81,52 @@
 		goto fail;
 	}
 
+	/* NOTE: We assume sighax is installed on firm0 */
+
+	sector = partitionGetSector(installPath);
+
 	uiPrintTextAt(0, 4, "Updating...\n");
 	
+	firmwriterInit(sector, fwSize / 0x200, true);
+	
+	for(size_t i=0; i<fwSize / 0x200; i++)
+	{
+			if(!firmwriterIsDone())
+			{
+				/* Write one sector in each iteration and update ui */
+				if(!firmwriterWriteBlock())
+				{
+					uiPrintError("Failed writing block!");
+					goto fail;
+				}
+			}
+			else
+			{
+				if(!firmwriterFinish())
+				{
+					uiPrintError("Failed writing block!");
+					goto fail;
+				}
+
+			}
+        
+			uiPrintTextAt(1, 20, "\r%"PRId32"/%"PRId32", i, fwSize / 0x200);
+
+			uiPrintProgressBar(10, 80, 380, 20, i, fwSize / 0x200);
+
+			
+ 
+	}
+
+	/* We should be done now... */
+
+	
+
+
+	uiPrintInfo("Press any key to reboot...");
+	menuWaitForAnyPadkey();
+
+	panic();
 	
 fail: