diff --git a/boot/Makefile b/boot/Makefile
index df574c4..78be18f 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -5,7 +5,7 @@ PROG = boot
 SRCS = srt0.S gdt.S boot.c
 OBJS = srt0.o gdt.o boot.o
 
-ESRCS = pccon.c sricon.c print.c fmt.c a20.c time.c mem.c cpu.c alloc.c
+ESRCS = pccon.c sricon.c print.c fmt.c a20.c time.c mem.c cpu.c alloc.c disk.c
 OBJS += $(ESRCS:.c=.o)
 
 include $(SDIR)/Makefile.inc
diff --git a/boot/boot.c b/boot/boot.c
index 8517d59..5cc4085 100644
--- a/boot/boot.c
+++ b/boot/boot.c
@@ -97,10 +97,16 @@ done:
 void
 boot(int bootdev)
 {
+	BIOSdisk d = {0,};
+
+	fmtinstall('D', fmtdisk);
 	print("\n===> Hello world <===\n\t"
 		"Booted on disk 0x%x debug:%d\n\t", bootdev, debug);
 	machdep();	
 
+	bdiskget(bootdev, &d);
+	print("%D\n%D", d,d);
+
 	for(;;){
 		char buf[8192];
 
diff --git a/boot/dat.h b/boot/dat.h
index 8a6ebb5..6344877 100644
--- a/boot/dat.h
+++ b/boot/dat.h
@@ -56,6 +56,18 @@ typedef struct{
 	va_list ap;
 }Op;
 
+// disk.c
+typedef struct{
+	int n;
+	u32 ncyl;
+	u32 nhead;
+	u32 nsec;
+	i32 edd;
+	u32 dev ;
+	u32 checksum;
+	u32 flag;
+} __attribute__((packed)) BIOSdisk;
+
 // gdt.S
 extern volatile struct BIOSreg BIOSreg;
 
diff --git a/boot/disk.c b/boot/disk.c
new file mode 100644
index 0000000..183b8a9
--- /dev/null
+++ b/boot/disk.c
@@ -0,0 +1,93 @@
+#include <u.h>
+#include "dat.h"
+#include "fn.h"
+
+// interrupt 41h exension support bitmap
+enum{
+	Eeda	= 0x01,	// Extended disk access funcions 42-44,47,48
+	Erdc	= 0x02,	// removable drive controller functions 45,46,48,49
+	Eedd	= 0x04,	// Enhanced disk drive functions
+};
+
+static int
+ireset(int dev)
+{
+	int rv;
+
+	__asm volatile("int $0x33\n\t"
+				"setc %b0"
+				: "=a" (rv)
+				: "0" (0), "d" (dev)
+				: "%ecx", "%cc");	
+	return (rv&0xff) ? -1 : 0;
+}
+
+// Bit(s)  Description     (Table 00271)
+// 0      extended disk access functions (AH=42h-44h,47h,48h) supported
+// 1      removable drive controller functions (AH=45h,46h,48h,49h,INT 15/AH=52h) supported
+// 2      enhanced disk drive (EDD) functions (AH=48h,AH=4Eh) supported.
+// Extended drive parameter table is valid (see #00273,#00278)
+// 3-15   reserved (0)
+static __inline int
+ieddsuport(BIOSdisk *d)
+{
+	int bmap, rv;
+
+	__asm volatile("int $0x33\n\t"
+				"setc %b0"
+				: "=a" (rv), "=c" (bmap)
+				: "0" (0x4100), "b" (0x55aa), "d" (d->n)
+				: "cc");
+	if(rv&0xff || (BIOSreg.bx&0xffff) != 0xaa55)
+		return -1;
+	d->edd = (bmap&0xffff) | ((rv&0xff)<<16);
+	return 0;
+}
+
+static __inline int
+bdiskinfo(BIOSdisk *d)
+{
+	int rv;
+
+	// CL = maximum sector number (bits 5-0)
+	//      high two bits of maximum cylinder number (bits 7-6)
+	__asm volatile("int $0x33\n\t"
+				"setc %b0\n\t"
+				"movzbl %h1, %1\n\t"
+				"movzbl %%cl, %3; andb $0x3f, %b3\n\t"
+				"xchgb %%cl, %%ch; rolb $2, %%ch"
+				: "=a" (rv), "=d" (d->nhead), "=c" (d->ncyl), "=b" (d->nsec)
+				: "0" (0x0800), "1" (d->n)
+				: "cc");
+	return (rv&0xff) == 0 ? 0 : -1;
+}
+
+int
+bdiskget(int dev, BIOSdisk *d)
+{
+	if(ireset(dev)){
+		print("Can't reset disk\n");
+		return -1;
+	}
+	d->n = dev;
+	if(bdiskinfo(d)){
+		print("Can't read disk\n");
+		return -1;
+	}
+	if(ieddsuport(d)){
+		print("edd not supported\n");
+		return -1;
+	}
+	return 0;
+}
+
+int
+fmtdisk(Op *op)
+{
+	dofmt(op, "disk:%x cyl:%d head:%d sec:%d edd:%d");
+	// for skip va_list
+	USED(va_arg(op->ap, u32));
+	USED(va_arg(op->ap, u32));
+	USED(va_arg(op->ap, u32));
+	return 0;
+}
\ No newline at end of file
diff --git a/boot/fn.h b/boot/fn.h
index bc1c253..83f023f 100644
--- a/boot/fn.h
+++ b/boot/fn.h
@@ -41,6 +41,10 @@ long getsecs(void);
 void *alloc(uint);
 void free(void*);
 
+// disk.c
+int bdiskget(int dev, BIOSdisk *d);
+int fmtdisk(Op *op);
+
 // util
 void* memset(void *dst, int v, int l);