parted boot loader code?

[Chris Murphy]

What is, and why does parted insert ~80 bytes of code to the MBR boot loader 
region of a disk when that region contains zeros?
Example:

address@hidden liveuser]# dd if=/dev/sda count=1 2>/dev/null | hexdump -C
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000200

## LBA 0 is all zeros.


address@hidden liveuser]# parted /dev/sda mklabel msdos
Information: You may need to update /etc/fstab.

address@hidden liveuser]# dd if=/dev/sda count=1 2>/dev/null | hexdump -C
00000000  fa b8 00 10 8e d0 bc 00  b0 b8 00 00 8e d8 8e c0  |................|
00000010  fb be 00 7c bf 00 06 b9  00 02 f3 a4 ea 21 06 00  |...|.........!..|
00000020  00 be be 07 38 04 75 0b  83 c6 10 81 fe fe 07 75  |....8.u........u|
00000030  f3 eb 16 b4 02 b0 01 bb  00 7c b2 80 8a 74 01 8b  |.........|...t..|
00000040  4c 02 cd 13 ea 00 7c 00  00 eb fe 00 00 00 00 00  |L.....|.........|
00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001b0  00 00 00 00 00 00 00 00  64 0b 00 00 00 00 00 00  |........d.......|
000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
00000200
address@hidden liveuser]#


## LBA 0 now contains code were there was previously none. The problem with it 
I'm encountering with a single BIOS so far (Virtual Box) is that this disk is 
no longer skipped at boot time, the BIOS tries to boot from it and hangs.


Chris Murphy