Subject: after fdisk'ing SCSI, can't boot DOS (was Re: big IDE disks (and DOS stuff - ugh!))
To: Gordon Ross <gwr@mc.com>
From: Wayne Berke <berke@panix.com>
List: port-i386
Date: 01/03/1995 11:54:58
I'm not sure if my problem is related or not.

I'm trying to get NetBSD and DOS to coexist on an AST Pentium box with
a 730M Quantum Lightning SCSI2 disk (NCR 53C810 card).

Installing NetBSD was a breeze - very good installation documentation, I
must say.

However, I didn't prepare the NetBSD partition with pfdisk beforehand so
the install script informed me of that fact, then overwrote the internal DOS
partition table.

Still no problems so far.  The rest of the install went without a hitch,
but I wanted to repartition the disk correctly before setting up NetBSD on a
permanent basis.  When I found out about pfdisk, I figured I'd boot off
the DOS floppy, use fdisk/pfdisk to repartition the hard drive with
the correct sys_ids for both DOS and NetBSD, reboot to format the
DOS partition, then re-install NetBSD.

The only problem is, after I use either fdisk or pfdisk to create a new
primary partition (with no errors), I can no longer boot DOS, even from
the floppy.  My boot disk (MSDOS 6.20) gets as far as printing
"Starting MS-DOS", then just hangs (with both floppy and hard drive
lights off).  This happens whether I partitioned the whole disk for DOS
or just part of it.

Paradoxically, the only way I can now get it to boot off a DOS floppy is to
first re-install NetBSD!  But then I'm back to square one.

Has anyone else seen this kind of thing?  The guys at AST recommended
various useless things like doing an "fdisk /mbr" and clearing the EISA CMOS
before partitioning.  None of this made any difference.  Maybe I need some
low level disk formatter/editor?

Interestingly enough, right after installing NetBSD and booting DOS, fdisk
and pfdisk both tell me that there's a single 24M partition (50,000 sectors)
at the beginning of the disk with the 165 sys_id.  It doesn't matter what
parameters I had previously given to the install program: how big I want
the NetBSD partition, the offset, even the size of the overall disk.  Nor
does it matter how I've partitioned the disk before installing NetBSD.  No
matter what I do, after the NetBSD install fdisk always sees a single
partition with size 24M.

This is how the partition looks under pfdisk (my real geometry according
to NetBSD is 3657 x 4 x 97).

	pfdisk> # Partition table on device: 0
	geometry 88 256 63 (cyls heads sectors)
	#  ID  First(cyl)  Last(cyl)  Name  # start, length (sectors)
	1   0      0          0       empty # 0, 0
	2   0      0          0       empty # 0, 0
	3   0      0          0       empty # 0, 0
	4 165      0          3       unkno # 0, 50000
	# note:  last(4): phys=(1023,255,63) logical=(3,25,41)
	# note: first(4): phys=(0,0,1) should be (0,1,1)
	active: 4
	pfdisk> 

Thanks in advance for any insights, and

Happy New Year!

======================================================================
Wayne Berke
berke@panix.com