From aswNS@hamp Wed Jun 28 22:46:48 1995
Date: Wed, 21 Jun 95 10:29:17 EDT
From: aswNS@hamp
To: Stephanos Ormrod 
Cc: aswNS@hamp
Newsgroups: comp.os.minix
Subject: Re: XT Installation Problems

In article <3s870f$8in@pirates.cs.swt.edu> you wrote:

: I have an old XT with 640k RAM and one 360k floppy.
: I have downloaded the i86 disk set and am trying to 
: load up Minix. The only disk that fits onto a 360k
: floppy is TINYROOT. What should I do to circumvent 
: this problem?

You don't mention a hard disk. You'll need 20M or more of hard disk
space to install the whole distribution. You can probably do some
useful work on a much smaller partition, but you won't have room for
source files and thus will find it hard to recompile the system. 

If you don't have a hard disk you will find it difficult to do much
with Minix on such a limited machine. If you can get access to another
machine with a lot of RAM and start up the system with a big RAM disk
you can use that system to copy a subset of the USR files to a 360K
TINYUSR disk.  Since the boot monitor makes possible to make a very
large ramdisk you can do this without installing Minix on the other
system -- you just need a RAM disk big enough to load all the commands
from the ROOT and USR disks. With TINYROOT and a TINYUSR You'll be
able to use your XT to familiarize yourself with the basics of a
UNIX-like system, but it won't be possible to do much work on it. Four
years ago it was possible to recompile the Minix system on an XT with
two floppies and no hard drive, but Minix 1.7 has become bigger as an
inevitable side effect of becoming better. Also, please keep in mind
that the prime purpose of Minix is to support teaching operating
systems with a system that students can modify and recompile as they
experiment with different approaches to various aspects of operating
systems. At this point it is not expected that universities will
have such limited equipment as you have.

If that XT is all you can afford, I suggest you get a hard disk for
it.  Currently on the East Coast of the US it is easy to find used
XT-style hard disks for from US$.50 to US$1.00 per megabyte -- i.e.,
with luck you can pick up a 40M disk for $20. You might have to throw
in another $5.00 for a used controller. This stuff is now considered
obsolete, and costs a fraction of what it cost new. If you have a
little more money you might look for a better macine, it's not hard to
find a used AT with a hard disk for less than US$200.

When you do get a hard disk I'm sure you'll be able to install Minix.
You'll still need to use another system with either (1) a large RAM,
so you can make a large ramdisk or (2) Minix installed on a hard disk.
On this you can convert the current distribution on 720K disks to 360K
disks. For each disk you need to do the following (This assumes fd0 is
a 3.5" drive and fd1 is a 5.25" drive):

Read in the disk with dd:
	dd if=/dev/fd0 of=tempfile count=1440
copy the first 360K to a 5.25" disk:
	dd if=tempfile of=/dev/fd1 count=720
put a new 3.5" disk in the drive and copy the second part:
	dd if=tempfile of=/dev/fd1 skip=720 count=720.
Repeat this for all the USR.n and SRC.n disks to make a full set. 
You can then use the 360K disks  to do the installation, substituting
360 for 720 as a parameter to the vol command.

In doing the installation you will find a bit of juggling and
reconstruction of the boot disk is necessary in order to get all the
programs you need to partition the hard disk and make file systems
accessible during the process. Once you get as far as getting
partitions made and the root installed on one you'll find it gets
easier.

With only 640K of memory you'll find using 200K for a ramdisk leaves
not much RAM for programs and data, so you will probably want to
forego the ramdisk and have your root on the hard disk. You'll find 
recompiling will take a long time, but it should be possible. 

Disclaimer: I haven't tried any of this, but I do have Minix 1.5
installed on an XT with a hard disk and I have recompiled it there. I
think it will be possible to do so with Minix 1.7, also.  I recommend
you redirect compiler messages to a log file, so you can look at them
later.  Then find a good book and a comfortable chair. Or else start
the compilation before you go to bed in the evening. :-)

--
Albert S. Woodhull, Hampshire College, Amherst, MA
awoodhull@hampshire.edu
woodhull@shaysnet.com
413-549-2962