Stage 1 boot issue?

[GoogleCodeExporter]

What steps will reproduce the problem?

In VirtualBox, setup a vmdk for a bootable USB drive as SATA port 1 and  
virtual hard disk vdi as SATA port 0. Install grub4dos to USB drive.

I used DavidB's VMUB utility to set this up.

SATA 0 = virtual disk vdi
SATA 1 = USB vmdk for bootable grub4dos USB drive

Start VBox VM and press F12 to get into BIOS boot select menu

press 2 to boot from the USB drive

RESULT:

'Missing MBR-Helper'

What is the expected output? What do you see instead?

Should boot to grub4dos

What version of the product are you using? On what operating system?

0.4.5c Jan 2014

Please provide any additional information below.

I checked using MBR code and  DL=81h  when MBR is called.
Therefore VBox behaviour looks correct.
Looking at Stage 1 MBR code of grub4dos, DL is preserved so I don't understand 
why it doesn't work.

Original issue reported on code.google.com by Steve6375 on 27 Apr 2014 at 6:33

[GoogleCodeExporter]

on a real machine, the boot drive number for normal floppy or harddrive is 
always 00 or 80h. so 81h is considered an invalid boot drive number. the 
grldr.mbr will ignore the dl register and insist on using 80h and 00 to locate 
the helper sectors. I could not say vbox is wrong, but I would like to treat it 
as rather different than a real machine. and I think this issue can be ignored.

Original comment by tinyb...@gmail.com on 28 Apr 2014 at 5:37

[GoogleCodeExporter]

So if I choose to boot from internal Hard drive 2 on a normal BIOS, are you 
saying that it uses DL=80h and not DL=81h?
If so then VBox is wrong.

Original comment by Steve6375 on 28 Apr 2014 at 7:07

[GoogleCodeExporter]

yes,  at least it appears to be yes.

but you cannot conclude that vbox is wrong. it depends on how the wrong is 
defined. If I recall it correctly, there is a standard or specification which 
allows boot drive number to be other than 00 and 80h.

Original comment by tinyb...@gmail.com on 29 Apr 2014 at 12:37