1 Aug
2026
1 Aug
'26
11:49 a.m.
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