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Difference(s) between DECtape and LINCtape

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Rich Alderson

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Nov 3, 2003, 8:45:59 PM11/3/03
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I have been studying the implementation of DECtape (555/TU55/TU56, *not* TU58)
for several months now, and I need a pointer to a detailed discussion of the
difference(s) in actual data written on the medium between this and LINCtape.

I think I know that the tape direction is opposite that of DECtape, but that's
not really relevant since either drive can read in either direction. Further,
there is some information in the LINC-8 manual on-line at Al Kossow's archives
regarding the mark words on the tape, but what I need to know is whether the
same values were used on LINCtape as on DECtape (55, 25, 26, 32, 10, 70, 73,
51, 45, 22).

Can someone confirm this for me? Or tell me where I can find out for myself?

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Rich Alderson | /"\ ASCII ribbon |
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David Gesswein

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Nov 4, 2003, 7:33:24 AM11/4/03
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In article <mddn0bc...@panix5.panix.com>,

Rich Alderson <ne...@alderson.users.panix.com> wrote:
>
>
>I have been studying the implementation of DECtape (555/TU55/TU56, *not* TU58)
>for several months now, and I need a pointer to a detailed discussion of the
>difference(s) in actual data written on the medium between this and LINCtape.
>
See

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm=aek-0601020821080001%40il0502a-dhcp193.apple.com&rnum=1&prev=/groups%3Fq%3Dlinctape%2Bformat%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26selm%3Daek-0601020821080001%2540il0502a-dhcp193.apple.com%26rnum%3D1

David Gesswein
http://www.pdp8.net/ -- Run an old computer with blinkenlights
Have any PDP-8 stuff you're willing to part with?

Rich Alderson

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Nov 4, 2003, 3:59:18 PM11/4/03
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My thanks to David Gesswein for the pointer to the PDP-12 documentation at the
bitsavers.org site; the system handbook in turn pointed me to the maintenance
manuals for details, which I have.

My thanks also to my old friend who got in touch by e-mail; I'll be contacting
him off-line.

Quick summary: All DECtape uses 6-bit longitudinal markers, and since the
introduction of the PDP-5 has written data horizontally across three (six pair-
wise redundant) tracks. LINCtape, on the other hand, uses 4-bit longitudinal
markers and writes data longitudinally:

DECtape LINCtape
------- --------
Data 1 0 3 6 9... 0 1 2 3
Data 2 1 4 7 10... 4 5 6 7
Data 3 2 5 8 11... 8 9 10 11

(The ellipses on the DECtape model reflect its use on 16-, 18-, and 36-bit as
well as 12-bit systems.)

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