--- //depot/user/jhb/boot/sys/boot/i386/zfsboot/zfsboot.c
+++ /home/jhb/work/p4/boot/sys/boot/i386/zfsboot/zfsboot.c
@@ -138,8 +138,8 @@
     unsigned unit;
     unsigned slice;
     unsigned part;
-    unsigned start;
     int init;
+    daddr_t start;
 };
 static char cmd[512];
 static char kname[1024];
@@ -163,7 +163,7 @@
 static void printf(const char *,...);
 static void putchar(int);
 static uint32_t memsize(void);
-static int drvread(struct dsk *, void *, unsigned, unsigned);
+static int drvread(struct dsk *, void *, daddr_t, unsigned);
 static int keyhit(unsigned);
 static int xputc(int);
 static int xgetc(int);
@@ -310,7 +310,8 @@
 vdev_read(vdev_t *vdev, void *priv, off_t off, void *buf, size_t bytes)
 {
 	char *p;
-	unsigned int lba, nb;
+	daddr_t lba;
+	unsigned int nb;
 	struct dsk *dsk = (struct dsk *) priv;
 
 	if ((off & (DEV_BSIZE - 1)) || (bytes & (DEV_BSIZE - 1)))
@@ -964,7 +965,7 @@
 #endif
 
 static int
-drvread(struct dsk *dsk, void *buf, unsigned lba, unsigned nblk)
+drvread(struct dsk *dsk, void *buf, daddr_t lba, unsigned nblk)
 {
 #ifdef GPT
     static unsigned c = 0x2d5c7c2f;
@@ -999,7 +1000,7 @@
     v86.es = VTOPSEG(buf);
     v86.eax = lba;
     v86.ebx = VTOPOFF(buf);
-    v86.ecx = lba >> 16;
+    v86.ecx = lba >> 32;
     v86.edx = nblk << 8 | dsk->drive;
     v86int();
     v86.ctl = V86_FLAGS;
--- //depot/user/jhb/boot/sys/boot/i386/zfsboot/zfsldr.S
+++ /home/jhb/work/p4/boot/sys/boot/i386/zfsboot/zfsldr.S
@@ -80,10 +80,10 @@
 
 		.org 0x25,0x90
 /*
- * Trampoline used by boot2 to call read to read data from the disk via
+ * Trampoline used by zfsboot to call read to read data from the disk via
  * the BIOS.  Call with:
  *
- * %cx:%ax	- long    - LBA to read in
+ * %ecx:%eax	- long    - LBA to read in
  * %es:(%bx)	- caddr_t - buffer to read data into
  * %dl		- byte    - drive to read from
  * %dh		- byte    - num sectors to read
@@ -94,10 +94,8 @@
 /*
  * Setup an EDD disk packet and pass it to read
  */
-xread.1:					# Starting
-		pushl $0x0			#  absolute
-		push %cx			#  block
-		push %ax			#  number
+xread.1:	pushl %ecx			# Starting absolute block
+		pushl %eax			#  block number
 		push %es			# Address of
 		push %bx			#  transfer buffer
 		xor %ax,%ax			# Number of
@@ -245,10 +243,11 @@
 /*
  * Trampoline used to call read from within boot1.
  */
-nread:		xor %ax,%ax			# Sector offset in partition
+nread:		xor %eax,%eax			# Sector offset in partition
 nread.1:	mov $MEM_BUF,%bx		# Transfer buffer
-		add 0x8(%si),%ax		# Get
-		mov 0xa(%si),%cx		#  LBA
+		xor %ecx,%ecx			# Get
+		addl 0x8(%si),%eax		#  LBA
+		adc $0,%ecx
 		push %cs			# Read from
 		callw xread.1	 		#  disk
 		jnc return			# If success, return