1 Aug
2026
1 Aug
'26
12:58 p.m.
Dave Gesswin should have a bronze statue for all the things he does....
Interestingly enough this brings up a point: I recently dumped some RX02
floppies using virtual devices in RSX11M+ for a person and he had a
devil of a time getting them to read on SIMH. Finally figured out that
SIMH was expecting 2 interleave and RSX didn't do that on the virtual
images.
I wonder if the interleave would be preserved if I used pdpgui and
dumped them that way, but I have a bunch of RX02 disks with neat things
like TSX+, SATURN software, and stuff like that. Maybe it's time for
Simh to support logical devices with 1-1 interleaves through an attach
option.
Thoughts? I'll stick them on www.crystel.com/pdp of course, but at the
same time I have lots of other stuff to do.
CZ
On 8/1/26 16:19, Bill Degnan via cctalk wrote:
Dave Gesswein constructed electronics to read the tape
data into his laptop
directly from a TU56. We backed up a pdp8, 11, and 10 tape all with the
same process. Dave used a program that I think Vince Briel created, but I
don't know who for sure, to view the tracks individually after import.
This program would show which tracks were all 00's and which were data.
The number of 00 tracks demonstrates whether the tape is 12, 16, 18 bit but
I don't recall exactly how this is done other than to count how many
columns were all 00's. We also viewed wave forms of the data as it was
being inputted.
I also have a TU56 but I have not used it yet. I did some research on the
drive and an interesting negibus/posibus conversion cable that was
apparently used to connect this TU56 to a PDP 9, more info here
https://www.vintagecomputer.net/browse_thread.cfm?id=788
I hopefully will get my TU56 up and running eventually. I donated the
adapter to the RICM a few years ago.
Bill
On Sat, Aug 1, 2026 at 3:49 PM Paul Koning <paulkoning(a)comcast.net> wrote:
>
>> On Aug 1, 2026, at 3:00 AM, Bill Degnan via cctalk <
> cctalk(a)classiccmp.org> wrote:
>> I dont' know. I watched as Dave Gesswein ran them through his TU56.
> Did he use read-all mode to read the raw tape structure? Or is this
> something lower level still, without using a TC11 controller?
>
>> I was
>> able to load the pdp8 and pdp11 tape
>> images using simH, I have not
>> yet tried the pdp10 tape image. The TU56 is a universal drive and as I
>> underatand it (barely), and if I understand correctly the tracks of 00's
>> are ignored and/or are used to indicate what kind of system made them,
> 12,
>> 16, or 18 bit.
> True. I remember a DECtape manua, perhaps the TC11/TU56 technical manual,
> with an appendix that shows the PDP-n DECtapes for all n, and the matrix of
> interoperabiltiy. So if you have a PDP-4 and needed to read PDP-11
> DECtapes, it would tell you whether that's possible.
>
> DECtapes basically have a clock track, a "mark" track, and 3 data tracks,
> all of these replicated. And controllers like the TC11 have a "read-all"
> mode where pretty much everything is extracted, I'm having some trouble
> finding out the precise details of how that deals with the block
> delimiters, block numbers, etc.
>
> The one thing a TC11 can't handle is LINCtape, because its low level
> encoding is different. I think the drive can handle it if you capture the
> waveforms, it's compatible at that level, but the controller even in
> read-all mode can't cope.
>
> paul
>
>