This is a low level tech question, as I develop the driver for the FDC at its command set level.
Having reviewed a number of sources I can not find the algorithm of how to format the 360k diskette using newer 1.2M drive. Lots talking about the differences in track size, magnetic material, how to degauss the media. But none lays out the algorithm in where heads must be positioned and in what order.
The goal is having diskette formatted using 1.2M drive to be portable to 360k drive as much as possible. I do not have 360k drive, thus can not perform try-and-fail to empirically find out the best way dealing with formatting.
I had formatted two 360k diskettes using Windows XP machine recently, and noticed the distinct behavior: heads start at track 0, to somewhere at the 1/2 of the surface towards the center in double track step, then heads go back about 20 tracks, and perform formatting in single track step up to the position where they retracted, and then continue as usual in double track step. This happened on two diskettes, thus it is not caused by the media defect.
There must be some explanation of this behavior, and formatting the 360k disk on 1.2M drive may not be that straightforward as go from outer to inner in double track step and write (format) tracks. What can, and must I do using floppy disk controller to format 360k diskette?