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IBM/Xebec HDD Controller - Head Stepping Pulses


By 'IBM/Xebec HDD Controller', I am referring to the hard drive controller that Xebec made for IBM's use in the IBM 5160 (IBM XT).

The following image shows an example of head step pulses being sent by the IBM/Xebec HDD Controller to whatever hard drive is attached.
In the example, a group of 5 pulses is being sent.

ibm_xebec_step_pulses.bmp


As can be seen, the IBM/Xebec HDD Controller generates step pulses of:
    * Step pulse width of 17 µs
    * Step pulse rate of 70 µs

Not all hard drives have step timing requirements that are compatible with the above. The Seagate ST-506 is an example. Such drives will not step properly.