5 Aug
2021
5 Aug
'21
12:57 p.m.
On Aug 5, 2021, at 8:39 AM, Jay Jaeger via cctech
<cctech at classiccmp.org> wrote:
I know Paul well (we were contemporaries at U. WI).
He does not
do that very often. He did not indicate any issue with a fire at the
building that contains his collection when I last spoke with him.
He does not actually read "blocks". He reads the tape in an
*analog*
fashion, and then processes the results with software. That
is how he recovered the IBM 1410 system tapes and diagnostics, for example.
To be honest, I doubt that this content would be such that he
would be likely to
volunteer.
Some years ago, inspired by Paul Pierce's earlier program in Java, I
wrote similar software in C to decode the analog waveforms from tapes
in a variety of formats: 7-track NRZI, 9-track NRZI, PE, and 6250 BPI
GCR, and 6-track NRZI for Whirlwind.
https://github.com/LenShustek/readtape
As a one-time physics major, I *am* interested in the Schoonschip
content. I've offered to James Liu to give it a go if he can't get
someone like Chuck to read it in a more straightforward fashion.
5 Aug
5 Aug
1:12 p.m.
On Aug 5, 2021, at 3:57 PM, Len Shustek via cctalk
<cctalk at classiccmp.org> wrote:
I remember reading that -- nice piece of work indeed. Around the same time I also saw a
project along the same lines in Poland, which recovered an interesting body of software
for various early Polish machines.
One of these days we hope to read some 10-track 1/2 inch tapes from an Electrologica X1, a
very odd format that could be described as "DECtape with variable length
blocks".
paul
On Aug 5, 2021, at 8:39 AM, Jay Jaeger via cctech
<cctech at classiccmp.org> wrote:
I know Paul well (we were contemporaries at U. WI). He does not do that very often. He
did not indicate any issue with a fire at the building that contains his collection when I
last spoke with him.
He does not actually read "blocks". He reads the tape in an *analog* fashion,
and then processes the results with software. That is how he recovered the IBM 1410
system tapes and diagnostics, for example.
To be honest, I doubt that this content would be such that he would be likely to
volunteer.
Some years ago, inspired by Paul Pierce's earlier program in Java, I wrote similar
software in C to decode the analog waveforms from tapes in a variety of formats: 7-track
NRZI, 9-track NRZI, PE, and 6250 BPI GCR, and 6-track NRZI for Whirlwind.
https://github.com/LenShustek/readtape 
6 Aug
6 Aug
9:45 a.m.
On 8/5/2021 2:57 PM, Len Shustek via cctalk wrote:
Cool!
For completeness, here is a link to Paul's 7 track recovery software
info (which is what I believe you are referring to - there is also an
older version.)
http://piercefuller.com/collect/a7tv.html
On Aug 5,
2021, at 8:39 AM, Jay Jaeger via cctech
<cctech at classiccmp.org> wrote:
I know Paul well (we were contemporaries at U.
WI).? He does not do
that very often.? He did not indicate any issue with a fire
at the
building that contains his collection when I last spoke with him.
He does not actually read "blocks".? He reads the tape in an *analog*
fashion, and then processes the results with software.? That is how he
recovered the IBM 1410 system tapes and diagnostics, for example.
To be honest, I doubt that this content would be such that he would
be likely to
volunteer.
Some years ago, inspired by Paul Pierce's earlier program in Java, I
wrote similar software in C to decode the analog waveforms from tapes in
a variety of formats: 7-track NRZI, 9-track NRZI, PE, and 6250 BPI GCR,
and 6-track NRZI for Whirlwind.
https://github.com/LenShustek/readtape
As a one-time physics major, I *am* interested in the Schoonschip
content. I've offered to James Liu to give it a go if he can't get
someone like Chuck to read it in a more straightforward fashion.
There is also this one for 9 track drives:
https://github.com/jakubfi/ninetracklab
(There is an article out on the 'net that points to this project,
referencing use of a logic analyzer to capture the data, but today I am
having trouble finding it with my searching spells.)
JRJ
10:01 a.m.
On 8/6/21 9:45 AM, Len via cctalk wrote:
The advantage of digitizing the output of the head preamp with a
https://usd.saleae.com/products/saleae-logic-pro-16 is you can do software
AGC and sometimes do eyeball recovery of dropouts.
Disadvantage is for a long tape you need >128gb of RAM as a capture buffer, and even
with lossless compression the captured data files
are quite large. The Saleae is also pretty expensive, but work really well.
Some years
ago, inspired by Paul Pierce's earlier program in Java, I wrote similar software in C
to decode the analog waveforms from tapes
in a variety of formats: 7-track NRZI, 9-track NRZI, PE, and 6250 BPI GCR, and 6-track
NRZI for Whirlwind.
https://github.com/LenShustek/readtape
10:21 a.m.
At 11:45 AM 8/6/2021, Jay Jaeger via cctalk wrote:
On 8/5/2021 2:57 PM, Len Shustek via cctalk wrote:
> > On Aug 5, 2021, at 8:39 AM, Jay Jaeger via cctech <cctech at
classiccmp.org> wrote:
> > I know Paul well (we were contemporaries at U. WI).
Where did Paul work at UW-Madison? I don't recall him. I was on campus
from 1981 to 1985.
There is also this one for 9 track drives:
https://github.com/jakubfi/ninetracklab
Has anyone ever developed a method of reading a magnetic tape
with some sort of array of new sensors capable of the pre-1908s
densities and tracks? A fine array of Hall effect sensors?
At 6250 BPI the bits are pretty tiny, aren't they?
- John
10:27 a.m.
On Aug 6, 2021, at 1:21 PM, John Foust via cctalk
<cctalk at classiccmp.org> wrote:
At 11:45 AM 8/6/2021, Jay Jaeger via cctalk wrote:
That was done by a number of people using MR (magneto-resistive) heads. John Bordynuik
was one of them, years ago; some others have done likewise. Those heads were built by IBM
for high density tape cartridges; 6250 is low density for them. They have some nice
properties, from what I understand, one of them is that the output signal levels don't
depend on the tape speed as regular inductive heads do. So for old tape recovery you can
readily run at very low speeds if needed to protect fragile media.
paul
On 8/5/2021 2:57 PM, Len Shustek via cctalk
wrote:
>> On Aug 5, 2021, at 8:39 AM, Jay Jaeger via cctech <cctech at
classiccmp.org> wrote:
>> I know Paul well (we were contemporaries at U. WI).
Where did Paul work at UW-Madison? I don't recall him. I was on campus
from 1981 to 1985.
There is also this one for 9 track drives:
https://github.com/jakubfi/ninetracklab
Has anyone ever developed a method of reading a magnetic tape
with some sort of array of new sensors capable of the pre-1908s
densities and tracks? A fine array of Hall effect sensors?
At 6250 BPI the bits are pretty tiny, aren't they? 
11:37 a.m.
On 8/6/21 10:27 AM, Paul Koning via cctalk wrote:
That was done by a number of people using MR
(magneto-resistive) heads. John Bordynuik was one of them, years ago; some others have
done likewise. Those heads were built by IBM for high density tape cartridges; 6250 is
low density for them. They have some nice properties, from what I understand, one of them
is that the output signal levels don't depend on the tape speed as regular inductive
heads do. So for old tape recovery you can readily run at very low speeds if needed to
protect fragile media.
IBM 3490 - 36 track. The 3590 and later get silly numbers of tracks on
half-inch tapes. Don't know if the 18-track 3480 was MR, however.
11:43 a.m.
On 8/6/21 11:37 AM, Chuck Guzis via cctalk wrote:
IBM 3490 - 36 track. The 3590 and later get silly numbers of tracks on
half-inch tapes. Don't know if the 18-track 3480 was MR, however.
According to this report:
https://www.govinfo.gov/content/pkg/GOVPUB-C13-8243628c307c697d4f7e3ab72875…
the 3480 18-track head is indeed MR read, thin-film write.
--Chuck
7 Aug
7 Aug
6:18 a.m.
On 8/6/2021 12:21 PM, John Foust via cctalk wrote:
At 11:45 AM 8/6/2021, Jay Jaeger via cctalk wrote:
He was a student here in Madison before that timeframe, as was I.
On 8/5/2021 2:57 PM, Len Shustek via cctalk
wrote:
>> On Aug 5, 2021, at 8:39 AM, Jay Jaeger via cctech <cctech at
classiccmp.org> wrote:
>> I know Paul well (we were contemporaries at U. WI).
Where did Paul work at UW-Madison? I don't recall him. I was on campus
from 1981 to 1985.
- John
JRJ
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days inactive
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