[tom_]

360 KB/side was indeed the default for the Atari ST, but there were numerous tools (I think Fastcopy III was the one I usually used) to format with more sectors per track, and 10 sectors/track (so 400 KB/side) was the standard recommendation if you just wanted more data per disk and no hassle. More than 80 tracks was also an option, and 81 or 82 tracks was apparently also reliable. That never sat right with me though, so I didn't do it.

(18 sectors per track with 256 byte sectors is also possible with the 1770 series. This was one of the disk format options on the BBC Micro. Definitely not written a track at a time! There just wasn't the memory for that.)