The following tables outline the development during the 1957-1981 period of IBM technologies in key areas of magnetic head and its air bearing support, disk substrate and its coating, head positioning actuator, and read/write electronics. For background information about the products listed in these tables, visit this exhibit's Product profile section.

Year of First Shipment
Product Year
350 1957
1405 1961
1301 1962
1311 1963
2314 1966
3330 1971
3340 1973
3350 1976
3310 1979
3370 1979
3380 1981
Recording Density
Product Areal density (MB/in.²) Linear bit density (bpi) Track density (tpi)
350 0.002 100 20
1405 0.009 220 40
1301 0.026 520 50
1311 0.051 1025 50
2314 0.22 2200 100
3330 0.78 4040 192
3340 1.69 5636 300
3350 3.07 6425 478
3310 3.8 8530 450
3370 7.8 12134 635
3380 more than 12 15200 more than 80

Key Geometric Parameters (microin.)
Product Head-to-disk spacing Head gap lengh Medium thickless
350 800 1000 1200
1405 650 700 900
1301 250 500 543
1311 125 250 250
2314 85 105 85
3330 50 100 50
3340 18 60 41
3350 18 50 41
3310 13 40 25
3370 13 25 41
3380 more than 13 25 more than 25

Air bearing & magnetic element
Product Bearing type Surface Contour Slider material Core material Slider/core bond
350 hydrostatic flat A1 laminated mu-metal eproxy
1405 hydrostatic flat A1 laminated mu-metal eproxy
1301 hydrodynamic cylindrical stainless steel laminated mu-metal eproxy
1311 hydrodynamic cylindrical stainless steel laminated mu-metal eproxy
2314 hydrodynamic cylindrical ceramic ferrite eproxy
3330 hydrodynamic cylindrical ceramic ferrite glass
3340 hydrodynamic taper flat ferrite ferrite integral
3350 hydrodynamic taper flat ferrite ferrite integral
3310 hydrodynamic taper flat ferrite ferrite integral
3370 hydrodynamic taper flat ceramic film deposited
3380 hydrodynamic taper flat ceramic film deposited

Disk
Product Diameter (in.) Substrate thickness Rpm Fixed removable Data surfaces spindle
350 24 0.100 1200 fixed 100
1405 24 0.100 1200 fixed 100
1301 24 0.100 1800 fixed 100
1311 14 0.050 1500 removable pack 10
2314 14 0.050 2400 removable pack 20
3330 14 0.075 3600 removable pack 19
3340 14 0.075 2964 module 6
3350 14 0.075 3600 fixed 15
3310 8.3 0.075 3125 fixed 11
3370 14 0.075 2964 fixed 12
3380 14 more than 0.075 3620 fixed 15

Actuator
Product Access geometry Heads Positioning Final Position Actuators spindle (max. no.) Avg. seek time (ms)
350 x-y 2 heads/ actuator motor-clutch detent 3 600
1405 x-y 2 heads/ actuator motor-clutch detent 3 600
1301 linear radial 1 head/surface hydraulic detent 2 165
1311 linear radial 1 head/surface hydraulic detent 1 150
2314 linear radial 1 head/surface hydraulic detent 1 60
3330 linear radial 1 head/surface voice coil motor servo surface 1 30
3340 linear radial 2 heads/surface voice coil motor servo surface 1 25
3350 linear radial 2 heads/surface voice coil motor servo surface 1 25
3310 rotary 1 h/s voice coil (+sector) 1 27
3370 linear 2 h/s voice coil motor servo surface 2 20
3380 linear 2 h/s voice coil motor servo surface 2 16

Read/write electronics
Product Date (Kbytes/s) Enconding Detection Clocking
350 8.8 NRZI ampl 2 osc
1405 17.5 NRZI ampl 2 osc
1301 68 NRZI ampl clk trk
1311 69 NRZI ampl osc
2314 312 2 f peak vfo
3330 806 mfm delta vfo
3340 885 mfm delta vfo
3350 1198 mfm delta vfo
3310 1031 mfm delta vfo
3370 1859 2.7 delta clip vfo
3380 3000 2.7 delta clip vfo

* Sourced from J. M. Harker, D, W. Brede, R. E. Pattison, G. R. Santana and L. G. Taft., "A Quarter Century of Disk File Innovation," IBM Journal of Research and Development, Vol. 25, No. 5, September 1981, p. 678, table 1