*BSD News Article 5550


Return to BSD News archive

Newsgroups: comp.unix.bsd
Path: sserve!manuel!munnari.oz.au!uunet!stanford.edu!ames!sgi!rigden.wpd.sgi.com!rpw3
From: rpw3@rigden.wpd.sgi.com (Rob Warnock)
Subject: Re: 386BSD and IDE drives
Message-ID: <q86oajo@sgi.sgi.com>
Sender: rpw3@rigden.wpd.sgi.com
Organization: Silicon Graphics, Inc.  Mountain View, CA
Date: Thu, 24 Sep 1992 07:34:44 GMT
Lines: 40

terry@cs.weber.edu (A Wizard of Earth C) writes:
+---------------
| Since DOS can't access cylinders past 1024, this means a DOS partition
| would have to be before that -- thus either reducing the usable disk space,
| or making the 386BSD partition the second one rather than the first.  A
| problem in asboot.c means that not having the 386BSD partition first can
| mean it won't work.
+---------------

Unless you patch "asboot" with the location of the Unix "a" partition. I did
exactly that (with DOS "DEBUG" & a little "INT 13" coding), and now everything
runs just fine. My layout is:

#        size   offset    fstype   [fsize bsize   cpg]
  a:  2639872   294912    4.2BSD     1024  8192    16   # (Cyl.  144 - 1432)
  b:   131072   163840      swap                        # (Cyl.   80 - 143)
  c:  2639872   294912    unused        0     0         # (Cyl.  144 - 1432)
  d:  2934784        0    unused        0     0         # (Cyl.    0 - 1432)
  e:   163840        0       DOS        0     0         # (Cyl.    0 - 79)

that is, from the beginning of the disk: DOS, Unix swap, and then Unix root.
Note that only the DOS and Unix "a" partitions have entries in the DOS part-
ition table, since 386bsd assumes that the first Unix partition mentioned in
the DOS partition table is the Unix "a" partition.


-Rob

p.s. For those who insist on trying this at home (no guarantees), the
locations to patch in the 0.1 "asboot" image are bytes 0x60-63. What
you put there is the *Big*Endian (reversed from DOS) sector number of
the start of the "a" partition (that is, the sector number of "asboot"
itself).

-----
Rob Warnock, MS-9U/510		rpw3@sgi.com
Silicon Graphics, Inc.		(415)390-1673
2011 N. Shoreline Blvd.
Mountain View, CA  94043