Data Rate
Tape System Data Rate
Model Year (in/sec) (Charac./in.) (Charac./sec.)
726 1953 75 100 7,500
727 1955 75 200 15,000
729-III 1958 112.5 556 62,550
729-VI 1962 112.5 800 90,000
2401-6 1966 112.5 1,600 180,000
3420-7 1971 200 1,600 320,000
3420-8 1973 200 6,250 1,250,000


Effective Acceleration
Tape System Model Year Terminal velocity (in/s.) Effective acceleration (G) Actuator
726 1953 75 25 Moving coil and 4-bar linkage
729-I 1957 112.5 55 Prolay and pinch roller
729-III 1958 112.5 62 Prolay and pinch roller
2420-7 1965 200 400 Low-inertia motor with capstan as an extension of the amarture
3420-8 1973 200 520


Characters Per Dollars of Monthly Rental
Tape System Performance
726 17.6
727 27.3
729-III 69.5
729-IV 94.8
2401-6 216
2420-7 304
3420-7 478
3420-8 1,440


* J. P. Harris, W. B. Phillips, J. F. Wells and W. D. Winger, "Innovations in the Design of Magnetic Tape Subsystems," IBM Journal of Research and Development, Vol. 25, No. 5, September 1981, pp. 694, 697 and 698.