DECtape

DECtape, originally called Microtape, is a magnetic tape data storage medium used with many Digital Equipment Corporation computers, including the PDP-6, PDP-8, LINC-8, PDP-9, PDP-10, PDP-11, PDP-12, and the PDP-15.

[2] From a programming point of view,[1]: p.505 [3] because the system is block-oriented and allows random seeking, DECtape behaves like a very slow disk drive.

In turn, LINCtape's origin can be found in the magnetic tape system for the historic Lincoln Laboratory TX-2 computer, designed by Richard L. Best and T. C. Stockebrand.

DEC advertised the availability of these peripherals in March and May, 1963, and by November, planning was already underway to offer the product for the 12-bit PDP-5 and 36-bit PDP-6, even though this involved a change in recording format.

Upon its introduction, DECtape was considered a major improvement over hand-loaded paper tapes, which could not be used to support swap files essential for practical timesharing.

Early hard disk and drum drives were very expensive, limited in capacity, and notoriously unreliable, so the DECtape was a breakthrough in supporting the first timesharing systems on DEC computers.

The legendary PDP-1 at MIT, where early computer hacker culture developed, adopted multiple DECtape drives to support a primitive software sharing community.

Initially, COI offered LINC-tape drives for computers made by Data General, Hewlett-Packard and Varian, with only passing reference to its similarity to DECtape.

[18] When COI offered the LINC Tape II with support for the DEC PDP-8, PDP-11, Data General Nova, Interdata 7/32, HP 2100, Honeywell 316 and several other computers in 1974, the drive was priced at $1,995 and was explicitly advertised as being DECtape compatible.

[23][24] DECtape II was introduced around 1978 and has a similar block structure, but uses a much smaller 0.150 in (3.8 mm) tape[25] (the same width as an audio compact cassette).

The tape is packaged in a special, pre-formatted DC150 miniature cartridge consisting of a clear plastic cover mounted on a textured aluminum plate.

Because of its low cost, the TU58 was fitted to several different systems (including the VT103, PDP-11/24 and /44 and the VAX-11/730 and /750) as a DEC-standard device for software product distribution, and for loading diagnostic programs and microcode.

The first version of the TU58 imposed very severe timing constraints on the unbuffered UARTs then being used by Digital, but a later firmware revision eased the flow-control problems.

However, rapid advances in low-cost floppy disk technology, which had an inherent speed advantage, soon outflanked the DECtape II and rendered it obsolete.