Marcus Glocker <mglocker@nextron.ch> typed:
:Problem
:---------
:NT 4.0 is installed on the first disc with scsi id 0 (boot-disc).
:NetBSD is installed on the second disc with scsi id 2.
:
:I can boot NetBSD directly if I set the second disc bootable with the
:adaptec bios.
:What I want is that I can boot NetBSD with the NT boot loader. So I do
:on NetBSD:
:dd if=/dev/rsd1a of=bootsect.bsd bs=512 count=1
:I copy the file on a ms-dos floppy disc, boot NT, copy the file on the
:c:
:partition and do an entry in boot.ini:
:c:\bootsect.bsd="NetBSD"
:I reboot NT and choose in the NT boot loader the NetBSD entry and got
:the
:nice message:
:No bootable partition
:Why can I boot NetBSD directly from its disc, but not with the nt boot
:loader?
:I am sure the bootsect.bsd is not corrupted, because I created it about
:10 times!

I'd suggest that using the NT bootloader is only going to work if NetBSD
is on the first disk.  The bootblock written probably presumes that 
the BIOS is pointing to the correct disk and goes from there.  I guess
the file you would need to modify is
   src/sys/arch/i386/stand/lib/crt/bootsect/start_bootsect.S
and rebuild it somehow.  Look around the line starting with ``hd:''

1) not really remembering how it works, try:
  commenting out ``andl    $0xff, %edx'' and uncomment
  ``/*mov   $0x0080, %edx*/'' (changing 80 to 81 (which points to your
  second disk)).

2) You may need to have
      movb    $0x81, %ah
      int     $0x13
   at the start of ``hd:'' (though maybe not).

I hope you get it working (then I might try again and stop using dosboot
(especially since newer dosboot versions just crash my computer)).
-- 
Geoff Wing   <gcw@pobox.com>            Mobile : 0412 162 441
Work URL: http://www.primenet.com.au/   Ego URL: http://pobox.com/~gcw/