GS/OS: UniDisk 3.5" Drive Motor Noise

When using a UniDisk 3.5" with GS/OS you will notice something different: the drive light will flash about 2 times per second, and the motor will seem to be starting up. (With the more familiar ProDOS 16, the light flashed but the motor did not behave in this fashion.) This seemingly odd behavior is caused by a new feature of GS/OS.
GS/OS lets the application know when a disk is ejected or switched from the drive. In order for GS/OS to check for disk switch events it sends a small program to the controller located in the UniDisk 3.5". When this program executes, the UniDisk 3.5" get ready for a disk access, causing the drive light to turn on and start up the motor.

The disk switch event allows the application to check the drive before it writes out information and changes the directory. This change also allows the DISK CACHE desk accessory to function correctly with the UniDisk 3.5.
Published Date: Feb 20, 2012