64628f99_nical_Details_and_Instructions__Description
[Signal Name] RPM MODE [Description] 
This is a command from the host machine to operate the floppy drive at 360 RPM instead of 300 RPM. Overseas, the 3 1/2 drives prefer the 360RPM speed, as does the older domestic 5 1/4 floppy disk drive, so some drives were given the ability to change speeds. This has a direct effect on data rate, the number of bits per second seen by the controller. 300RPM can be considered 5 rotations per second, and 360RPM can be considered 6 rotations per second. This behavior also leads to being able to use 3 1/2 drives to replace 5 1/4 or 8 inch stock, as long as you match the RPM.
USB Floppy Disk Drive Converter/Emulator Technical Details and Instructions
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