TU58 yet one more time.

[Mattis Lind]

2016-05-29 20:10 GMT+02:00 Al Kossow <aek at bitsavers.org>:

>
>
> On 5/29/16 10:03 AM, Mattis Lind wrote:
>
> > Would it be possible to use a Floppy Tape (QIC-117) tape drive to read
> > them?
>
> No. The heads are movable on floppy tapes, and the format is completely
> different.
>

Yes. I am aware of that. But that also means that the head can be moved
into the spot where the information is recorded. My quick reading of the
QIC-117 spec give that the one control the drive with a quite weird
interface consisting of the STEP, TRACK ZERO and INDEX lines.

The READ DATA is supposed to be the actual flux transitions. Likewise is
WRITE DATA.

What is not yet clear to me is whether that the QIC-117 drive is rather
dumb and leaves most work to the FDC or if it includes a lot of logic to
handle the reading process.
http://www.qic.org/html/standards/11x.x/qic117j.pdf

The QIC36 drive that was used to recover the information stored on the
Zilog S8000 tapes is completely stupid. The read data just reflected the
flux transitions which AJ recorded using a logic analyzer so that it was
possible to decode the MFM data stream in software. The tracks of course
also differed since the QIC36 drive was 9 track while the DEI drive used
for recording the S8000 tapes used four (fixed) heads. But nevertheless it
was possible to recover the entire tape thanks to the circuitry that AJ
devised to control the head position. Using a more modern SCSI drive it
will not be possible to read these tapes since they only handle GCR
encoding (as does QIC02 drives)


Could this kind of operation be done with a QIC-117. I.e. is the drive
stupid enough? Reading more of the spec may indicate that "segment" concept
might be the culprit that makes it non-feasible. It could be that the drive
keeps track of the segments somehow.

Of course there is always the possibility of "hacking" the drive. But then
it would help with schematics which is probably not available for these
quite "modern" things.

All input appreciated!


> If you send me your address, I can send you a chunk of tubing that Brad
> Parker and I
> have used to repair the drive wheels.
>

That would be very nice. Send you a message off-list.

/Mattis