![]() You can see one such implementation in Roedy Green’s PARK which comes with source code, or in Jim Leonard’s disassembly of SpinRite’s PARK. Typically, this would attempt to move the heads past the last “official” cylinder (over an “engineering cylinder” on MFM and RLL drives), or, starting with ATs, use the landing zone specified in the BIOS drive parameter table (accessed using the vectors stored at interrupts 0x41 and 0x46). So early PCs had a PARK command which would park the heads away from the disk surface. For a long time now, the arms which hold the heads have been designed to “auto-park” the heads away from the disks’ surface, or over a safe “ landing zone”, when they lose power¹, but early (up to the mid 80s) hard drives didn’t have this feature, so their heads would land on the disk surface, which could sometimes damage the surface. ![]() When power is removed, the heads no longer fly. Hard drives have read/write heads which fly above the spinning disks when the drive is powered. ![]()
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