This is discbeast.

Discbeast is a disc utility for the BBC Micro series of computers. It drives
the disc controller chip directly to offer advanced read and write
functionality, supporting the 8271 and 1770/2 disc controllers.
Perhaps most usefully, it includes an "HFE Grab" command that can directly
and accurately read all known BBC disc protection schemes on systems with 1770/2
controllers. The resulting TRKS intermediate files can be reconstructed back
into the modern HFE format.


- Initialization and setup.
If you have a switchable 40/80 track drive, switch it to 80 tracks no matter
what discs you intend to look at.

The first command you need to supply is the INIT command to specify which
drive and surface to operate on. For example:

INIT 0
(The space is optional.)

Typical values for INIT will be 0-3 inclusive, mapping to the BBC's drive
numbers.
All being well, discbeast will report something like:

OK 1770
DRIVE 0 SPEED: 3125

It is assumed you have an 80 track drive. If you have a 40 track drive, specify:

DR40 1

If you are going to be capturing and saving discs with the HFE grab tool, you
need to set up where the resulting TRKS<n> files will be saved to. By default,
that will be drive 1 (and 3 for 80 track captures) of the DISC filing system.
If instead you wish to save to e.g. RAMFS, use:

FSYS RAM

This will execute *RAM before every *SAVE. Any FSYS string is passed verbatim
to a * command.


- 8271 vs. 1770 disc controller.

Both the 8271 and 1770/2 disc controllers have long lists of quirks and
headaches. But at the end of the day, the 1770 is better at seeing more of the
disc surface than the 8271.

Disc captures should be done with a 1770. (The 8271 capture code is less capable
at this time, and also much more experimental.)

Some examples of things the 1770 can see that the 8271 can't, or can't easily:
a) Accurate track length. (Western Security protection.)
b) Sectors where the header has a CRC error. (Elite duplication markers.)
c) Accurate first sector header start position.
d) Sectors with logical track 0, but not physical track 0.
e) Sectors with logical track 255.

The disc fingerprinting is designed so that it should work equally on an 8271
or 1770 based system. The 8271 implementation is, however, less mature.


- Basic commands.

TIME            - re-check and display drive rotation timing
SEEK 7          - seek to track 7
RIDS            - read and display sector headers of current track
READ 7 3 1 256  - read logical track 7, logical sector 3, 1 sector total,
                  with 256 byte sectors, and display result
DUMP &80        - dump latest read buffer from offset hex 0x80
RTRK            - read current track fully (1770 only)
DTRK            - dump details about current track


- Auto mode.
By default, with an 80 track drive, the fingerprinting and capture tools will
attempt to automatically detect 40 track vs. 80 track discs by having a little
look at a few odd numbered tracks. To turn it off, you can use:

AUTO 0

And then manually specify double stepping (40 track disc in an 80 track drive)
with:

DSTP 1


- Disc fingerprinting.

One of the primary goals of discbeast is to permit owners of original discs to
quickly "fingerprint" them to see if their disc is known to the community or
not. This is to assist in thorough archival of as many discs and variants as
possible.
In particular, at the time of writing, the BBC Micro community has not engaged
in a structured attempt at archiving original discs. This is a problem as many
original discs are becoming lost, or rotting away. 

This is the command to fingerprint a disc:

DCRC (auto)
DCRC 0 9 (specified track range, inclusive)

All being well, it'll crank away for a while, displaying a CRC for each track
and finally a grand total CRC such as:

DISC CRC32 DDDB3CB9

The fingerprint is based on the sector bytes for cleanly defined sectors (no
on-disc CRC errors, no sectors that an 8271 can't read). It doesn't include
inter-sector GAP bytes, or sector header bytes. The rationale here is that
any significant change in inter-sector GAP bytes is likely to also come along
with a significant change in the sector data to do the updated check.
Put another way, the CRC32 aims to be as simple as stable as possible while
still having great chances to catch any difference of significance.


- Disc capturing.

In an ideal world, we'd capture all variants of all BBC discs with accurate
modern solutions such as a GreaseWeazle.
However, not everyone has a GreaseWeazle. But a lot of people have BBCs with
disc drives as well as a collection of original discs. The good news is that
the BBC itself is capable of directly capturing protected discs -- even tricky
ones! (Even if a disc is protected, it still has to readable otherwise you have
problems.) When captured with a 1770 disc controller, the resulting images have
pretty good fidelity.

To capture a disc, make sure you've read the "Initialization and setup" section
above, particularly noting to switch your drive to 80 track mode no matter
what, and understanding where the capture files will be written.

Kicking off a capture is pretty easy:

HFEG (auto)
HFEG 0 40 (manual track range)
HFEG 0 40 0 (manual track range, do not save results)

A bunch of files starting with TRKS will be written, 8kB each and containing
2 tracks each. These TRKS files can be rebuilt into an HFE file with C program
hfeg2hfe.c. Just run that executable with the working directory set to where
the series of TRKS files reside.

TRKS files occupy more space that the source tracks, so if the destination
is another disc (a Gotek drive perhaps), plan appropriately. A 40 track capture
needs an 80 track destination disc, and an 80 track capture needs a double
sided 80 track destination disc.


- HFE Grab colors and symbols.

When capturing a disc, HFE Grab displays a colored symbol for each track
analyzed.
  Main symbols:
    Square blob              : normal data
    Letter 'D'               : at least one sector of deleted data
    Asterisk                 : track has sectors of different physical size
  Extra symbols:
    Exclamation (dark blue)  : no sectors found
    Exclamation (red)        : read error (will usually retry)
    Number '1' - '9'         : non-standard number of sectors (i.e. not 10)
    Plus                     : non-standard number of sectors (more than 10)
  Colors:
    Green                    : nothing remarkable
    Dark blue                : no sectors found
    Magenta                  : more than 2560 sector data bytes in track
    Red                      : sector CRC16 error (header or data)
    Yellow                   : sector physical / logical size mismatch
    Cyan                     : logical track 0 on non-physical track 0
    White                    : logical / physical track mismatch


- 40 track vs. 80 track discs.

Ideally, just use the default AUTO mode which will try and auto sense a 40
track vs. 80 track disc. If you think it's wrong, or you just like manual
control (AUTO 0), you can take the decision on yourself.

Deciding whether to perform a 40 track or 80 track capture can be an annoyance.
Some discs have a 40 track side and an 80 track side, making the decision easy.
Other discs only have a 40 track side. But a large number of discs have a single
side labeled 40/80 track compatible. This is often, but not always, a 40 track
surface with special code logic to seek extra steps as required.
If you do a 40 track capture and the underlying disc is really 80 track, you
might see a large patch of green blobs and a large patch of white blobs in the
graphical capture display.
If you do an 80 track capture and the underlying disc is really 40 track,
every other track might incur retries (beeb and red exclamation mark) or may be
noted as unformatted (dark blue with exclamation mark).


- Caveats.

When capturing a disc, discbeast might perform a large seek with a different
step rate than you are used to hearing. You disc drive could sound very
different! Do not worry, it is not broken.