Re: Extracting files off “unknown” 8 inch disks. Any thoughts…

[Terry Stewart]

>If it's an RX02 operating in double-density mode, you're not going to
>read the disks with any commodity floppy controller.  You will, however,
>get the sector ID headers.

>DEC used a rather peculiar scheme where headers were recording in
>single-density (FM), but the body of the sector (the data) is recorded
>in a "peculiar" MFM, that employs some pattern substitutions to avoid
>conflict with similar patterns in the headers.

Thanks Chuck

Hmm...I'll do some more checking with IMD and Anadisk tonight.  I haven't
looked at this disks in Anadisk yet.  IMD did recognise some things...maybe
it was the Sector ID headers.

Even if I can't get anything off, I'm now very curious as to exactly what
I'm dealing with.

Terry



On Fri, May 5, 2017 at 11:50 AM, Chuck Guzis via cctalk <
cctalk at classiccmp.org> wrote:

> On 05/04/2017 04:30 PM, js--- via cctalk wrote:
>
> > On 5/4/2017 6:16 PM, Terry Stewart via cctalk wrote:
> >>> If these are from a VAX, could they be microcode disks for a
> >>> 11/780?
> >> There was a RX01 attached via a LSI-11 as console.
> >
> > And yet, if there were an RX02 somewhere on this VAX, I don't
> > believe you'd be able to read them at all... RX02 seeming more likely
> > with a VAX.
>
> If it's an RX02 operating in double-density mode, you're not going to
> read the disks with any commodity floppy controller.  You will, however,
> get the sector ID headers.
>
> DEC used a rather peculiar scheme where headers were recording in
> single-density (FM), but the body of the sector (the data) is recorded
> in a "peculiar" MFM, that employs some pattern substitutions to avoid
> conflict with similar patterns in the headers.
>
> A catweasel will work just fine--and there's code out there to handle it.
>
> --Chuck
>
>
>
>
>