HP DC100
# HP DC100

The DC100 tape format and drive was developed by Hewlett-Packard and introduced as a data storage mechanism for the HP-9825 programmable calculator. The DC100 tape cartridge was a scaled-down version of the DC300 cartridge pioneered by 3M, and represents an early version of what is now referred to as the QIC Mini Cartridge

This format was used in the HP desktop calculator/computer systems of the late 1970s and early 1980s, including the 9815, 9825, 9845 and HP series 80. It was also used in the HP 2640 series of computer terminals.

The DC150 cartridge, a variation with slightly higher capacity, was used in Digital Equipment Corporation's DECtape II drives.

The DC100 tape is based on the 1972 patent number U.S. Patent 3,692,255.

| Generation | DC100 | DC300 |
| - | - | - |
| Release date | 1975 | 1972 |
| Native capacity | 210 kB | 2.9 MB |
| Max speed | 650 B/s | |
| Tape length | 140 ft (42.7 m) | 300 ft (91.4 m) |
| Tape width | 0.150 in (3.81 mm) | 0.25 in (6.35 mm) |
| Data density | 1600 bpi | |
| Tracks | 2 | |
| Coercivity | 310 Oe | |

Features from 3M:

* Base plate flatness.
* Guide posts (essentially the 5 "axles" in the cartridge) into the base plate with sufficient perpendicularity.
* Guide-post surface finish. Too rough, abraded the back of the tape. Too smooth, tape adheres to the guide through stiction, which causes speed flutter on the tape. The right surface treatment was found to be lapidary tumbler, a recipe of abrasive and burnishing compound.
* Guide-post perpendicularity had to be right to avoid differential tension on the tape. In the severe case contact between tape and head was lost. The two most critical guide posts in the manufacture fixture, the hub bearing or axle posts, had to be perpendicular to within approximately 1/3° degrees.
* Lubrication.
* Cartridge’s internal plastic drive belt (critical).

HP improvements on the 3M design:

* Tape tension is controlled primarily by friction in two rollers that the belt loops around. 3M controlled belt-roller friction (and hence the tape tension) with a very precise amount of STP lubricant on the bearing surfaces. A better design was to use large axles and Teflon-filled plastic for the bearing rollers, which eliminated the need for lubrication.
* Minimum tape tension at the head was increased, the drive force to spin the drive puck was less however.
* Optical sensing of cartridge in and write protect.
* DC200 tape cartridge used a thinner tape to increase the amount of data over DC100.

3M developed the DC300 tape cartridge for loading programs into AT&T’s electronic switching systems that were becoming the backbone of the world’s phone system in the 1970s.

QIC minicartridges evolved its capacity from 250 kByte, 40, 80, 120, to a final 250 MByte. QIC-3230 tapes have a 20 Gbyte maximum.

