Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss

Minix demo disk booting problems

157 views
Skip to first unread message

Grant Totten

unread,
Nov 24, 1992, 10:46:56 AM11/24/92
to

Hello Minixers,

I ftp'd the minix 1.5 demo disk with the intention of trying it
out on my (underpowered) PC at home. It is a generic clone 286 with
1MB RAM (640K, 384K), Hercules graphics, and an 80MB disk.

Well, I got the binary file (demon_dsk.ibm), the documentation,
and rawrite.exe. I then downloaded (in binary mode) this stuff to a
directory on my PC's hard drive. I then formatted a 360K 5 1/4 inch
disk and ran rawrite. I supplied rawrite with the filename (demo_dsk.ibm)
and the disk to write on (A:). It processed through the file and finished
with no errors. So then I <Ctrl-Alt-Del> rebooted with my new minix demo
boot floppy.

It started up with something like:

'Booting Minix 1.5 (c) 1991 Prentice-Hall'

Then a couple of seconds of floppy-reading... Then:

'Read error - Automatic reboot'

And it started booting over again. It keeps doing this forever. Yuck :(

I thought since it was a read error maybe the diskette was bad. So I
formatted another and went through the rawrite process again. Rebooted and
still the same problem.

I'd appreciate any ideas and/or suggestions you kind net.people can come
up with. My goal in trying all this is to see if it is feasible to run
Minix on my woefully underpowered PC at home. If it works and isn't TOO
slow, I'm going to get the 'full' version from Prentice-Hall.

Help! :)

Grant

Grant Totten, Programmer/Analyst, Trent University, Peterborough Ontario
GTo...@TrentU.CA Phone: (705) 748-1653 FAX: (705) 748-1246
========================================================================
Death is Nature's way of recycling human beings.

neb...@gmail.com

unread,
Mar 18, 2020, 11:33:50 AM3/18/20
to
Hello Minixers,

28 years later, I'm having the exact same problem, trying to get MINIX 1.5 to boot on the PCem emulator. Searching with google, this old thread is the ONLY thing that comes up about this!

I see from this other post ( https://groups.google.com/forum/#!msg/comp.os.minix/Cm72kXon9xs/LPhh7ABKBYEJ ) that Grant eventually got it to work, but not too many details are provided:

"First off, thanks to the kind people who helped me with my
booting problem with the Minix demo disk. All works well now - I just
had to format a disk for the 'native' mode of my 5 1/4" floppy, namely
1.2Mb and *NOT* 360K."

On the off chance that anyone still monitors this group, I thought I'd post and see if anyone remembers the details of that fix.

Giovanni

unread,
Mar 18, 2020, 1:10:59 PM3/18/20
to
On 03/18/2020 04:33 PM, neb...@gmail.com wrote:

It's a lot of time that I heard of Minix 1.5!!!

> "First off, thanks to the kind people who helped me with my booting
> problem with the Minix demo disk. All works well now - I just had to
> format a disk for the 'native' mode of my 5 1/4" floppy, namely 1.2Mb
> and *NOT* 360K."
>
> On the off chance that anyone still monitors this group, I thought
> I'd post and see if anyone remembers the details of that fix.

I never tried to install it on a emulator, but I did several
installations on emulators of Minix 2.0.4 and I did not have troubles.

I can only remember that Minix1.5 went on 5"1/4 floppies formatted for
360K that still lie in a box on a shelf at home. And as I remember
Minix 1.5 can only handle that format.

I think that what Grant says is that using the original format couldn't
boot but it had to copy the images on a 1.2M floppy. Maybe because of
its floppy drive, having problems with a the 360K format.

Usually for using the emulator I copy the floppies to files and use
those files as floppy images.

Ciao
Giovanni
--
A computer is like an air conditioner,
it stops working when you open Windows.
< http://giovanni.homelinux.net/ >

Paganini

unread,
Mar 19, 2020, 10:43:33 AM3/19/20
to
Hi Giovanni,

Thanks for replying. You were on the right track there! Turns out the minix 1.5 disk images are just of the filesystem, or something like that, so the files are variable in length, not 360k each. I had the drive set to 360k in PCem, but apparently PCem allows you to mount arbitrarily sized image files regardless of that setting. The root disk is only around 200k and MINIX tests disks by trying to read from the last sector. Since there was no last sector, it would reboot, try again, reboot, try again, etc. I just used dd to pad all the image files out to 360k and now they work fine.

Next problem… why does mkfs trash the partition table every time I run it? To the source mobile! Good thing I have lots of free time just now!

:)

On Wednesday, March 18, 2020 at 1:10:59 PM UTC-4, Giovanni wrote:

> It's a lot of time that I heard of Minix 1.5!!!
>

Giovanni

unread,
Mar 19, 2020, 11:51:52 AM3/19/20
to
On 03/19/2020 03:43 PM, Paganini wrote:

> Next problem… why does mkfs trash the partition table every time I
> run it? To the source mobile! Good thing I have lots of free time
> just now!

Glad you got to finish to the boot process!

Unfortunately I can't help with this new problem. What I remember is
Minix 1.5 having a peculiar problem. The /usr was on disk while the /
(root) filesystem was on ram and to be loaded after reboot. At first I
solved by loading from disk the content of the ram. When I learned
enough of Minix I booted from disk. making a few changes to the
configuration.

Unless you have the needs for a very, very small OS for 8086 real mode
why using Minix 1.5. I suggest to switch to a Minix 2.0 series. It is
more complete and can handle more memory. With a 2MByte memory
expansion Minix 2.0.2 worked smoothly on a 286PC. I still have a 1990's
toshiba that I use for portable terminal for my server (via serial
interface).

You can find the images in the Download -> Previous Version page at
http://www.minix3.org/

Also my website has the images at
http://giovanni.homelinux.net/minixV2/index.html

Paganini

unread,
Mar 19, 2020, 3:33:34 PM3/19/20
to
Hi Giovanni,

Well, this is a bit of a personal project for me. I don't have such old hardware that I *need* a 1.x version of MINIX (in fact, I have the version 2 CDROM that comes with the 2nd edition of the OSDI book).

Many (20+!) years ago I did part of a computer science degree at college. I took a different path and did not become an IT professional, but I still have my interest in computers.

Back in those days, I always felt like it was "cheating" to use a call like printf() if I didn't know what it was doing. My philosophy is that abstraction is good for production, but bad for learning! :) To feel like I really understand how things work, I want to be able to, for example, re-implement the standard library, from printf() to putchar() right down to OS system calls and the IN and OUT x86 instructions!

I think it is pretty impossible for one person to understand the entirety of a modern system. Just my Android phone has layers and layers of API and is billions of times more powerful and more complicated than those old 1980s systems.

Because of this, I've always liked the MINIX philosophy that a Version 7 UNIX system is the sweet spot in complexity for learning - it's powerful enough to actually be useful, but small enough that one person can comprehend the whole system right down to the bare metal I/O.

It's been on my bucket list for a while to fully grok an old 16 bit real-mode UNIX running on an IBM XT or AT or something similar. Thanks to the Pandemic Panic, right now I have a lot of extra free time. PCem is able to accurately emulate many of those old hardware configurations, so I can indulge my retro-computing fantasies without having to actually buy an old IBM AT from eBay! :D

BTW, my virtual 286 MINIX system now has two 20MB hard disks that are working! For some reason, MINIX does not seem to like the partition tables made by MINIX fdisk. I used the old Ranish "Partition Manager" DOS program to fix the hard disk images. MINIX mkfs seems to zero the bootblock (not sure why that is) but I have rebooted several times and the filesystems are still there. So... progress! :)

Giovanni

unread,
Mar 20, 2020, 5:19:15 AM3/20/20
to
On 03/19/2020 08:33 PM, Paganini wrote:
> BTW, my virtual 286 MINIX system now has two 20MB hard disks that are
> working! For some reason, MINIX does not seem to like the partition
> tables made by MINIX fdisk. I used the old Ranish "Partition Manager"
> DOS program to fix the hard disk images. MINIX mkfs seems to zero the
> bootblock (not sure why that is) but I have rebooted several times
> and the filesystems are still there. So... progress! :)

There is something wrong but I think I can't help you. I'm sure I never
had problems with the mkfs program and/or fdisk. I did even reimplement
fdisk a version for MSDOS based on MINIX source because I found it more
friendly than the fdisk native in DOS.

I agree on your approach, At that time (1993) I was working on a OS for
a telephone system and Minix was a teaching complement to my previous
experience. Nevertheless I still suggest You switch to a later version
than 1.5.

Fred J. Scipione

unread,
Mar 28, 2020, 3:39:09 AM3/28/20
to
[This followup was posted to comp.os.minix and a copy was sent to the
cited author.]

In article <c120c296-6e1c-4bd8...@googlegroups.com>,
neb...@gmail.com says...
>
> Hello Minixers,
>
> 28 years later, I'm having the exact same problem, trying to get MINIX
> 1.5 to boot on the PCem emulator. Searching with google, this old
> thread is the ONLY thing that comes up about this!
>
> I see from this other post
> ( https://groups.google.com/forum/#!
> msg/comp.os.minix/Cm72kXon9xs/LPhh7ABKBYEJ )
> that Grant eventually got it to work, but not too many details are
> provided:
>
... <snip> ...

Check the Google groups archives of comp.os.minix for "Scipione" and
"demo" around 1994-1995. Then check any minix code archives from the
same time frame for my 'Demo boot disk image' boot-sector fix.

Two possible problems -
1. Without my fixed boot sector, the demo image has no 'AA55' signature
(which the emulator start-up code may be rejecting), and the code in
the demo disk's boot sector makes calls to the IBM-PC ROM-BIOS (which
is probably different in the emulator from IBM's copyrighted binary).
My patched boot sector fixed both those problems.

2. The OS version in the Demo package had the '16-meg' bug. After
you get the boot sector to run, you may hit that problem next.

Also check out my post for the 'Getting Minix from the net Quiz' for
some hints on how to get around the Demo's other limitations :-).

If you cannot find my boot-sector fix, let me know and I will check
my private archives.

Paganini

unread,
Mar 28, 2020, 10:05:18 AM3/28/20
to
Hi Fred,

Thanks for your reply! I got the disks all sorted out. Turns out that MINIX 1.5 tries to figure out drive parameters by reading from the last sector of a disk. The disk images I had downloaded were different sizes, and all were shorter than a whole 360k floppy. I used dd to pad the images out to exactly 360k; after that they worked fine.

I do have an actual IBM AT BIOS (there's a huge ROM archive for PCem with a gazillion old BIOSes) but I'm not using it, since I don't have the IBM BIOS configuration disk. I'm just using a generic clone BIOS (I think it's AMI) that has a setup program.


On Saturday, March 28, 2020 at 3:39:09 AM UTC-4, Fred J. Scipione wrote:
...
0 new messages