It would have at least had to be the SA400-L, since
the SA400 was 35 track,
and PC-DOS, from the get-go, used 40 tracks.
Or [trivially] patched. Either done right, or kludged by putting a
non-existent file in the directory occupying tracks 35-39.
There were some strange patches in the early days!
PC-DOS 1.00 was single sided only, but the FDC supported double sided, and
double sided drives were very available. There was a patch being passed
around that would permit installing a double sided drive, and the second
side would be treated as though it were an additional drive. I never got
around to trying that with 4 drives installed, . . .
Does anybody know what the actual origin was for that patch?