DECtape was a magnetic tape storage medium used with early Digital Equipment Corporation computers, including the PDP-6, PDP-8, LINC, PDP-10, PDP-11, PDP-12, and the PDP-15. DECtapes were 3/4 inch wide and formatted into blocks of data that could be read or written individually. One tape stored 184K 12-bit PDP-8 words. Block size was 128 words. From a programming point of view, DECtape behaved like a very slow disk drive. DECtape was controversial for its amazing similarity to LINCtape, which was originally designed by Wesley A. Clark at the MIT Lincoln Laboratory as an integral part of the LINC computer. The design of the LINC, including LINCtape, was in the public domain, and LINCtape drives were manufactured by several companies, including Digital. DECtape appeared to many to have been "designed" by the simple process of systematically reversing every arbitrary design feature of LINCtape. Thus, LINCtape and DECtape had opposite placements of feed and takeup reels, wrote signals to tape with opposite magnetic polarities, and wrote the bits of a byte in different orders. These changes had no obvious engineering purpose other than to make LINCtape and DECtape different from each other. Mechanical dimensions, speeds, and signal characteristics were identical, and Digital's hybrid machines, such as the PDP-12, featured units were capable of operating in either a LINCtape or DECtape mode. Digital patented the DECtape; the patents were tested in court and ruled invalid. DECtape II was introduced around 1979 and had a similar block structure, but on a cartridge tape. The TU58 DECtape II controller had an RS232 serial interface, allowing it to be used with other computers, such as the Automatix Autovision machine vision system and AI32 robot controller. TU58 drivers are available for modern Personal computers. ==See also== * LINC#LINCTape - additional material on LINCtape lineage and operation ==External link== * [http://www.pdp8.net/tu56/tu56.shtml TU56 DECtape Drive Information] DEC hardware Computer storage tape media
I'm skeptical of the claim that DEC's US patent 3,387,293 on DECtape was invalidated. The patent covers aspects of DECtape that are nontrivially distinct from LINCtape. For instance, LINCtape was designed for bidirectional search, but DECtape was designed for bidirectional data transfer as well. This required a substantial change to the way the mark track was encoded. Google doesn't seem to have any other references to this patent being invalidated. Does anyone have a citation to the court case, or at least know who the plaintiff was? If not, I think it should be removed from this page and the LINC page. --User:Brouhaha 00:44, 19 Oct 2004 (UTC) ---- I'm putting back the reference to DECtapes on PDP-10s. The KA10 system that I grew up on definitely did have DECtapes. Also, the PIP10 utility on OS/8 was specifically designed to allow PDP-8s to read and write PDP-10 DECtapes. User:Atlant 18:22, 8 Dec 2004 (UTC) : Well, but not all PDP-10 models came with DECtapes. Alas, my ''decsystem10 Reference Manual'' doesn't explicitly say if all KA-10/KI-10 configurations included DECtapes as a standard, so I don't know about that. (According to the ftp://ftp.its.os.org/its/ai/system.tgz configuration file, only two of the three Incompatible Timesharing System KA's at MIT had DECtapes, for what that's worth.) The KL10-B models (TOPS-20) definitely did ''not'' include DECtapes. (KL-10A's had them, but they were attached to the console PDP-11 - not sure if any OS's for the KL10-A allowed access to them from the -10.) : The other thing is that according to the same book, PDP-1's, -4's and -7's had them too. In other words, they were probably an available I/O option for pretty much all PDP's, so to be technically accurate we'd have to list them all, which would look silly. : In leaving only the 6, 8, and 11 in the list I had tried to list the older, smaller machines for which they would have been a primary mass-storage device - with their small (~300KB) size, once larger disks arrived, they wouldn't even have been useful for backup. : I would be OK with an edited list which didn't list ''all'' the machines that supported them, but just the ones for which they were a ''primary'' mass-storage device. Otherwise let's just link to PDP and be done with it... User:Jnc User_talk:Jnc 15:17, 9 Dec 2004 (UTC) I've never seen a DECtape on a PDP-1, but if you say they existed, I believe you; this link certainly supports your contention: http://groups-beta.google.com/group/alt.folklore.computers/browse_thread/thread/ebf63b298ba975b6/1d820bc0c5328407?q=PDP-1+dectape&_done=%2Fgroups%3Fq%3DPDP-1+dectape%26start%3D10%26hl%3Den%26lr%3D%26&_doneTitle=Back+to+Search&&d#1d820bc0c5328407 as does another newsgroup posting from Bob Supnik, who'd certainly know. On the other hand, *EVERY* photo of a KA10 and every KA10 that I've seen first-hand had DECtapes, right up above and to the right the system console (not necessarily TU56 DECtapes; sometimes the older, relay-controlled TU55 DECtapes). It's a shame I don't have a copy of the Dick Best Options/Modules list any more. :) The PDP-1 apparently had the ancient 555 'tapes. In any case, I'd be in agreement with omitting the list of all supported platforms and just referring people out to a PDP page and, if people felt it necessary, the LINC page (although LINC is linked from the PDP page). User:Atlant 17:19, 9 Dec 2004 (UTC) The KI10 diagnostics were supplied on DECtape; I suspect that DEC would not offer service on a KI10 without DECtape, just as they later required that KL10 systems have an RP06 to be on service. Early KL10 diagnostics were also on DECtape, but they were supplanted by the KLAD pack. DECtape was not available until well after the introduction of the PDP-1, but was made available as an option for it. The PDP-1 being restored at the Computer History Museum includes an option to interface to an external Type 550 DECtape control. --User:Brouhaha 22:06, 9 Dec 2004 (UTC)
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Words begining with DECtape:
DECtape
DECtape
DECtape
DECtape was a magnetic tape storage medium used with early Digital Equipment Corporation computers, including the PDP-6, PDP-8, LINC, PDP-10, PDP-11, PDP-12, and the PDP-15. DECtapes were 3/4 inch wide and formatted into blocks of data that could be read or written individually. One tape stored 184K 12-bit PDP-8 words. Block size was 128 words. From a programming point of view, DECtape behaved like a very slow disk drive. DECtape was controversial for its amazing similarity to LINCtape, which was originally designed by Wesley A. Clark at the MIT Lincoln Laboratory as an integral part of the LINC computer. The design of the LINC, including LINCtape, was in the public domain, and LINCtape drives were manufactured by several companies, including Digital. DECtape appeared to many to have been "designed" by the simple process of systematically reversing every arbitrary design feature of LINCtape. Thus, LINCtape and DECtape had opposite placements of feed and takeup reels, wrote signals to tape with opposite magnetic polarities, and wrote the bits of a byte in different orders. These changes had no obvious engineering purpose other than to make LINCtape and DECtape different from each other. Mechanical dimensions, speeds, and signal characteristics were identical, and Digital's hybrid machines, such as the PDP-12, featured units were capable of operating in either a LINCtape or DECtape mode. Digital patented the DECtape; the patents were tested in court and ruled invalid. DECtape II was introduced around 1979 and had a similar block structure, but on a cartridge tape. The TU58 DECtape II controller had an RS232 serial interface, allowing it to be used with other computers, such as the Automatix Autovision machine vision system and AI32 robot controller. TU58 drivers are available for modern Personal computers. ==See also== * LINC#LINCTape - additional material on LINCtape lineage and operation ==External link== * [http://www.pdp8.net/tu56/tu56.shtml TU56 DECtape Drive Information] DEC hardware Computer storage tape media
DECtape
I'm skeptical of the claim that DEC's US patent 3,387,293 on DECtape was invalidated. The patent covers aspects of DECtape that are nontrivially distinct from LINCtape. For instance, LINCtape was designed for bidirectional search, but DECtape was designed for bidirectional data transfer as well. This required a substantial change to the way the mark track was encoded. Google doesn't seem to have any other references to this patent being invalidated. Does anyone have a citation to the court case, or at least know who the plaintiff was? If not, I think it should be removed from this page and the LINC page. --User:Brouhaha 00:44, 19 Oct 2004 (UTC) ---- I'm putting back the reference to DECtapes on PDP-10s. The KA10 system that I grew up on definitely did have DECtapes. Also, the PIP10 utility on OS/8 was specifically designed to allow PDP-8s to read and write PDP-10 DECtapes. User:Atlant 18:22, 8 Dec 2004 (UTC) : Well, but not all PDP-10 models came with DECtapes. Alas, my ''decsystem10 Reference Manual'' doesn't explicitly say if all KA-10/KI-10 configurations included DECtapes as a standard, so I don't know about that. (According to the ftp://ftp.its.os.org/its/ai/system.tgz configuration file, only two of the three Incompatible Timesharing System KA's at MIT had DECtapes, for what that's worth.) The KL10-B models (TOPS-20) definitely did ''not'' include DECtapes. (KL-10A's had them, but they were attached to the console PDP-11 - not sure if any OS's for the KL10-A allowed access to them from the -10.) : The other thing is that according to the same book, PDP-1's, -4's and -7's had them too. In other words, they were probably an available I/O option for pretty much all PDP's, so to be technically accurate we'd have to list them all, which would look silly. : In leaving only the 6, 8, and 11 in the list I had tried to list the older, smaller machines for which they would have been a primary mass-storage device - with their small (~300KB) size, once larger disks arrived, they wouldn't even have been useful for backup. : I would be OK with an edited list which didn't list ''all'' the machines that supported them, but just the ones for which they were a ''primary'' mass-storage device. Otherwise let's just link to PDP and be done with it... User:Jnc User_talk:Jnc 15:17, 9 Dec 2004 (UTC) I've never seen a DECtape on a PDP-1, but if you say they existed, I believe you; this link certainly supports your contention: http://groups-beta.google.com/group/alt.folklore.computers/browse_thread/thread/ebf63b298ba975b6/1d820bc0c5328407?q=PDP-1+dectape&_done=%2Fgroups%3Fq%3DPDP-1+dectape%26start%3D10%26hl%3Den%26lr%3D%26&_doneTitle=Back+to+Search&&d#1d820bc0c5328407 as does another newsgroup posting from Bob Supnik, who'd certainly know. On the other hand, *EVERY* photo of a KA10 and every KA10 that I've seen first-hand had DECtapes, right up above and to the right the system console (not necessarily TU56 DECtapes; sometimes the older, relay-controlled TU55 DECtapes). It's a shame I don't have a copy of the Dick Best Options/Modules list any more. :) The PDP-1 apparently had the ancient 555 'tapes. In any case, I'd be in agreement with omitting the list of all supported platforms and just referring people out to a PDP page and, if people felt it necessary, the LINC page (although LINC is linked from the PDP page). User:Atlant 17:19, 9 Dec 2004 (UTC) The KI10 diagnostics were supplied on DECtape; I suspect that DEC would not offer service on a KI10 without DECtape, just as they later required that KL10 systems have an RP06 to be on service. Early KL10 diagnostics were also on DECtape, but they were supplanted by the KLAD pack. DECtape was not available until well after the introduction of the PDP-1, but was made available as an option for it. The PDP-1 being restored at the Computer History Museum includes an option to interface to an external Type 550 DECtape control. --User:Brouhaha 22:06, 9 Dec 2004 (UTC)
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DA | DB | DC | DE | DF | DG | DH | DI | DJ | DK | DL | DM | DN | DO | DP | DR | DS | DT | DU | DW | DX | DY | DZ |Words begining with DECtape:
DECtape
DECtape
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