Re: [TUHS] PL/I stuff - was: Book Recommendation

Re: [TUHS] PL/I stuff - was: Book Recommendation

[Noel Chiappa]

    > From: "Charles H. Sauer"k <sauer@technologists.com>

    > I haven't done anything with 9 ktrack tapes for a long time ...
    > I don't recall problems reading any of them. ...
    > IMNSHO, it all depends on the brand/formulation of the tape. I've been 
    > going through old audio tapes and digitizing them 

The vintage computer community has considerable experience with old tapes; in
fact Chuck Guzis has a business reading them (which often includes converting
old file formats to something modern software can grok).

We originally depended heavily on the work of the vintage audio community, who
pioneered working with old tapes, including the discovert of 'baking' them to
improve their mechanical playability. ("the binder used to adhere the magnetic
material to the backing ... becomes unstable" - playing such a tape will
transfer much of the magnetic material to the head, destroying the tape's
contents.)

It's amazing how bad a tape can be, and still be readable. I had a couple of
dump tapes of the CSR PWB1 machine at MIT, which I had thoughtlessly stored in
my (at one period damp) basement, and they were covered in mold - and not just
on the edges! Chuck had to build a special fixture to clean off the mold, but
we read most of the first tape. (I had thoughtfully ade a second copy, which
read perfectly.)

Then I had to work out what the format was - it turned out that even though
the machine had a V6 filesystem, my tape was a 'dd' of a BSD4.1c filesystem
(for reasons I eventually worked out, but won't bore you all with). Dave
Bridgham managed to mount that under Linux, and transform it into a TAR
file. That was the source of many old treasures, including the V6 NCP UNIX.

      Noel

Re: [TUHS] PL/I stuff - was: Book Recommendation

[Charles H Sauer]

On 11/27/2021 9:25 AM, Noel Chiappa wrote:
>      > From: "Charles H. Sauer"k <sauer@technologists.com>
> 
>      > I haven't done anything with 9 ktrack tapes for a long time ...
>      > I don't recall problems reading any of them. ...
>      > IMNSHO, it all depends on the brand/formulation of the tape. I've been
>      > going through old audio tapes and digitizing them
> 
> The vintage computer community has considerable experience with old tapes; in
> fact Chuck Guzis has a business reading them (which often includes converting
> old file formats to something modern software can grok).
> 
> We originally depended heavily on the work of the vintage audio community, who
> pioneered working with old tapes, including the discovert of 'baking' them to
> improve their mechanical playability. ("the binder used to adhere the magnetic
> material to the backing ... becomes unstable" - playing such a tape will
> transfer much of the magnetic material to the head, destroying the tape's
> contents.)

The notion of "baking" is slightly misleading. When done with audio 
tapes, the practice is to use a dehydrating oven at about 130F for about 
24 hours.

> It's amazing how bad a tape can be, and still be readable. I had a couple of
> dump tapes of the CSR PWB1 machine at MIT, which I had thoughtlessly stored in
> my (at one period damp) basement, and they were covered in mold - and not just
> on the edges! Chuck had to build a special fixture to clean off the mold, but
> we read most of the first tape. (I had thoughtfully ade a second copy, which
> read perfectly.)
> 
> Then I had to work out what the format was - it turned out that even though
> the machine had a V6 filesystem, my tape was a 'dd' of a BSD4.1c filesystem
> (for reasons I eventually worked out, but won't bore you all with). Dave
> Bridgham managed to mount that under Linux, and transform it into a TAR
> file. That was the source of many old treasures, including the V6 NCP UNIX.
> 
>        Noel
> 

-- 
voice: +1.512.784.7526       e-mail: sauer@technologists.com
fax: +1.512.346.5240         Web: https://technologists.com/sauer/
Facebook/Google/Twitter: CharlesHSauer

Re: [TUHS] tape "baking" [was PL/I stuff - was: Book Recommendation

[Charles H Sauer]

On 11/27/2021 9:53 AM, Charles H Sauer wrote:

> The notion of "baking" is slightly misleading. When done with audio 
> tapes, the practice is to use a dehydrating oven at about 130F for about 
> 24 hours.

Ampex patent 5,236,790 says 54C for 16 hours.

-- 
voice: +1.512.784.7526       e-mail: sauer@technologists.com
fax: +1.512.346.5240         Web: https://technologists.com/sauer/
Facebook/Google/Twitter: CharlesHSauer

Re: [TUHS] tape "baking" [was PL/I stuff - was: Book Recommendation

[Steve Nickolas]

On Sat, 27 Nov 2021, Charles H Sauer wrote:

> On 11/27/2021 9:53 AM, Charles H Sauer wrote:
>
>> The notion of "baking" is slightly misleading. When done with audio tapes, 
>> the practice is to use a dehydrating oven at about 130F for about 24 hours.
>
> Ampex patent 5,236,790 says 54C for 16 hours.

That's 129F, so pretty much the same diff.

-uso.

Re: [TUHS] tape "baking" [was PL/I stuff - was: Book Recommendation

[Al Kossow]

On 11/27/21 8:07 AM, Steve Nickolas wrote:

>> Ampex patent 5,236,790 says 54C for 16 hours.

There are a few other tricks, like forcing air through the tape during baking
that we came up with in the 00s. There are others, like using 32 track 3490 MR
head stacks for recovery.

80's Memorex is some of the worst tape ever made, it was also the cheapest, and way
too many distribution and backup tapes were made using it.

Re: [TUHS] tape "baking" [was PL/I stuff - was: Book Recommendation

[Al Kossow]

On 11/27/21 9:39 AM, Al Kossow wrote:
> On 11/27/21 8:07 AM, Steve Nickolas wrote:
> 
>>> Ampex patent 5,236,790 says 54C for 16 hours.
> 
> There are a few other tricks, like forcing air through the tape during baking
> that we came up with in the 00s. There are others, like using 32 track 3490 MR
> head stacks for recovery.
> 

https://patents.google.com/patent/CA2817359A1