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Setting Up a New Drive (Profiling Tool)

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Disk Change/Ready (line 34)

The preferred mode for the Applesauce is READY.

Many drives have a jumper to select the meaning of line 34, DISK CHANGE/READY (DCRY)1)2)3):

  • In READY mode, line 34 becomes goes low after the motor has turned on and two index holes have passed. This means that a disk is present and that the drive is up to speed. This is from the original Shugart specification and is usually required for XT systems.
  • In DISK CHANGE mode, line 34 goes low when a disk is ejected and goes high again when the head moves successfully. This is a modification from IBM and is usually required in AT systems.

The Applesauce will work correctly with either setting. During drive setup, the Profiling tool will try to automatically detect the signal the drive is sending. If the drive sends READY, then the Applesauce will wait for READY after the MOTOR ON signal before doing anything else. If the drive sends DISK CHANGE, then the Applesauce will wait a fixed amount of time after the MOTOR ON signal. (Otherwise, DISK CHANGE is ignored.)

Thus, in READY mode, you can typically save a couple of hundred milliseconds on MOTOR ON.4) The other option is carefully examining the drive's data sheet to find its maximum ready time.