Imaging and Emulating Rainbow

Warner Losh imp at
Sun Aug 14 12:43:20 CDT 2016

On Sun, Aug 14, 2016 at 11:35 AM, Rob Jarratt
<robert.jarratt at> wrote:
>> > Oh dear. VMS would not let me MOUNT/FOREIGN, it said:
>> >
>> >     %MOUNT-F-FORMAT, invalid media format
>> >
>> > So I couldn't mount it to do the BACKUP/PHYSICAL.
>> >
>> > What options do I have to image this disk?
>> >
>> >
>> It appears that the format used by the Rainbow disk controller is not
>> compatible with the format used by the controller in the MVII :-(
>> It looks likely you will have to run something on the Rainbow itself to do
> this
>> unless it is possible to extract the disk controller from the Rainbow and
> put it
>> into something else that can cope with it.
> I should have thought of that. I think my options are either on-box, or
> David Gesswein's MFM reader/emulator. My inclination is the latter because I
> actually bought the original board but then never actually built it because
> at the time I was enjoying the challenge of attempting to create my own such
> reader/emulator using an FPGA. My project faltered and I never found the
> energy to build David's, but I think I will now.

The format used by the Rainbow and the MVII are the same. The low-level, bits
on the disk format. However, the Rainbow and the MVII use radically
different meta
data to describe the disks (both in terms of how tracks are
constructed and some other
bits). The source to the Rainbow hard disk partitioning and formatting
utility is
available in the various Rainbow archives. You'd need to start there.
It has extensive
documentation about all the details of how things are put down onto
the drive to 'format'

I've successfully read, but not written rainbow hard drives with an
ancient version
of FreeBSD that supported the ST-504 interface and the WD8002
controller. FreeBSD
killed that code a long time ago, but I think it may still be alive in
Linux. It's been so
long I don't recall if it was a simple dd, or if I had to hack
something together to read
the raw bytes off each track...  Looking just now, I can't find the
images I created, but
I still have my Rainbow 100B (upgraded to a 100+) in the basement.


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