I spent another night with Robert Nordier's UNIX V7 port to the x86 architecture (http://www.nordier.com/v7x86/index.html).
The first attempt had been a few months before on a real 32-bit netbook with a real spinning harddisk and a primary partition. The V7 system booted from the CDROM on a USB-attached drive just fine. But since the USB drive is not an ATAPI drive as assumed by the V7/x86, the installation process failed. (It would have been so nice to have the V7 right next to the Solaris10 on the same disk...)
This time I tried an installation in a proxmox VM, the ISO image
being attached as a virtual IDE/ATAPI drive. (I had fired up
ron running a proxmox installation just yesterday to
check its version; I was pleasently surprised that I was at the
same major release as a customer whom I need to support now.)
The V7/x86 installation ISO allows to escape into a shell in
order to partition the target disk with a ptdisk
utility. I then ran into the issue which I eventually found
documented in http://www.nordier.com/v7x86/files/ISSUES.
I was able to extract the missing /boot/mbr from
the CDROM and run the ptdisk using it. This allowed
the installation to run. However, the resulting MBR wouldn't boot
the system from the (virtual) disk afterwards.
I guess it's a C/H/S geometry issue. I toyed around a bit before giving up. My next attempt would be to boot another OS on this VM to fdisk the disk, then try again with the V7/x86 install (as advised in the mentioned ISSUES page).
Summary:
Lots of dd and od today... and also
echo * because: the v7 ls is strictly
-1.