Re: Minix 1.1 with QEMU

[John Snow]

On 9/23/20 1:00 PM, Will Senn wrote:
> On 9/23/20 11:53 AM, Philippe Mathieu-Daudé wrote:
> > Hi Will,
> >
> > On 9/23/20 6:45 PM, Will Senn wrote:
> > > Long time user, first time poster :)
> > >
> > > So, I'd like to be able to run Minix 1.1 on my Macbook Pro mid-2012
> > > w/16gb RAM (MacOS 10.14.6 Mojave). Qemu will run pretty ancient OS'es
> > > such as DOS 2.0, which I use all of the time. However, I'm having some
> > > difficulty getting Minix to run. I am able to boot the first floppy, but
> > > when I change to the second floppy, the system freezes and I can't tell
> > > what is going on. Here's what I did to get this far:
> > >
> > > brew install qemu
> > >
> > > qemu-system-i386 --version
> > > QEMU emulator version 5.1.0
> > >
> > > mkdir ~/workspaces/retro-workspace/minix-1.1
> > > cd ~/workspaces/retro-workspace/minix-1.1
> > > aria2c
> > > http://download.minix3.org/previous-versions/bzipped/Intel-1.1.tar.bz2
> > > tar xvjf Intel-1.1.tar.bz2
> > > cp Intel-1.1/floppy_disk1 ./Disk01.img
> > > cp Intel-1.1/floppy_disk2 ./Disk02.img
> > > cp Intel-1.1/floppy_disk3 ./Disk03.img
> > > cp Intel-1.1/floppy_disk4 ./Disk04.img
> > >
> > >
> > > qemu-system-i386 -drive
> > > file=Disk01.img,format=raw,if=floppy,media=disk,readonly=off,index=0,snapshot=on
> > > \
> > >    -boot a \
> > >    -no-fd-bootchk \
> > >    -monitortelnet::2222,server,nowait  -serial mon:stdio
> > >
> > > Qemu boots to the Minix 1.1 Boot screen and says to swap to floppy 2, so
> > > in the monitor:
> > > change floppy0 Disk02.img raw
> > >
> > > I press l (el) and it scans the disk, lists the files on the disk and
> > > reports no errors, but when I press =, it does a carriage return and
> > > just sits there. I'm pretty sure this is the Minix going bye bye and not
> > > necessarily QEMU, but I'm wondering if there is a way to see what QEMU
> > > thinks it is doing or if it is what's hung? Usually, at this point,
> > > Minix reads the disk contents into a Ramdisk and boots Minix.

You can turn on tracing! See docs/devel/tracing.txt for more. You can 
also run QEMU under GDB and break on floppy functions to see what's 
going on if you are so inclined.

> > > Food for thought... Minix expects to run on an IBM PC (5150), IBM PC XT
> > > (5160), or compatible, and therefore the I/O is written for whatever
> > > floppy controller was extant at that time (I'm guessing here), so if
> > > that's different than modern day floppies, I suppose this could cause
> > > the problem I'm experiencing here. Is there a way to see the floppy
> > > controller activity in QEMU? Similarly, I gather it expects a CGA
> > > compatible monitor (EGA/VGA, etc should be fine).
> > Can you try adding '-machine isapc', which is closer to the 5150?
> >
> > > I appreciate your help on this.
> > >
> > > Minix 1.1 works 'ok' in 86Box and other IBM PC emulations, so I know the
> > > floppies are fine.
> > >
> > > Thanks!
> > >
> > > Will
> > >
> > >
> > >
> > > --
> > > GPG Fingerprint: 68F4 B3BD 1730 555A 4462  7D45 3EAA 5B6D A982 BAAF
> Phillipe,
>
> My new incantation is:
>
> qemu-system-i386 -machine isapc -drive 
> file=Disk01.img,format=raw,if=floppy,media=disk,readonly=off,index=0,snapshot=on 
> -boot a   -no-fd-bootchk   -monitor telnet::2222,server,nowait -serial 
> mon:stdio
>
> with the same outcome :(. Thanks for the suggestion, I'll keep it in 
> mind for other projects.
>
> Will
>
> --
> GPG Fingerprint: 68F4 B3BD 1730 555A 4462  7D45 3EAA 5B6D A982 BAAF

This isn't the first time I've seen a report of floppy disks behaving 
poorly in older operating systems.

I'm afraid I don't have the time to really investigate these issues, but 
I am happy to take patches.

--js