IBM 729
| Company type | Product |
|---|---|
| Industry | Computer storage |
| Predecessor | IBM 727 |
| Headquarters | United States |
| Products | Magnetic tape storage units |
| Parent | IBM |
The IBM 729 Magnetic Tape Unit served as IBM's chief magnetic tape storage solution throughout the late 1950s until the mid-1960s. Belonging to the IBM 7-track series, it was compatible with late models of the 700 and most 7000 computers as well as numerous machines in the IBM 1400 series. Similar to its forerunner, the IBM 727, the 729 utilized magnetic tape reels up to in length and in diameter. To facilitate swift tape acceleration and minimize access delays, vacuum columns were installed between the reels and read/write heads; these columns absorbed tension fluctuations that might otherwise damage the tape. Write protection was achieved by a detachable plastic ring fitted onto the reel.
Data format
The tape comprised seven parallel tracks—six dedicated to data and one assigned for parity checking. For character data encoded in BCD, even parity was employed, while binary tapes utilized odd parity. Physical markers indicating the start and end of the tape consisted of aluminum strips positioned near its edges. A 3/4-inch space separated records, allowing sufficient time for the tape mechanism to halt. The initial operating speed was 75 inches per second (2.95 m/s) with a recording density of 200 characters per inch, resulting in a payload transfer rate of 90 kbit/s (rising to 105 kbit/s when including parity bits). Subsequent models supported increased densities up to 800 characters per inch and speeds reaching 112.5 in/s, enabling payload throughput up to 540 kbit/s (630 kbit/s raw). At a density of 200 characters per inch, a single tape measuring 2400 feet could hold roughly four million six-bit bytes—approximately three million octets or the equivalent of 50,000 punched cards.
Eventually, the 729 series was superseded by 9-track tape drives introduced alongside the IBM System/360.
Models
- 729 I: Released for use with the IBM 709 and IBM 705 III, this model resembled the IBM 727 but incorporated vacuum tubes and a dual gap head enabling write verification.
- 729 II: Designed for the transistor-based IBM 7000 series, featuring a new cabinet design and supporting dual recording densities (200 and 556 characters per inch).
- 729 III: Offered high-speed operation at 112.5 in/s with single density recording at 556 characters per inch.
- 729 IV: Combined high-speed performance (112.5 in/s) with dual density capability (200 and 556).
- 729 V: Focused on high-density recording at 800 characters per inch.
- 729 VI: Delivered both high speed (112.6 in/s) and high density (800), introduced in September 1961.
See also
- IBM 7330, an economical alternative seven-track tape drive
References
- IBM 709 Data Processing System, Form A22-6501-0