Normally, all sort options (/SNAME, /SEXT, /SUDATE) implicitly sort first by DEVICE+PPN. Adding /SNODEV to another sort option removes the implicit primary sort on DEVICE, and /SNOPPN removes the secondary sort on PPN. For example:

.DIR ALL:[]/SNAME                  ; by DEVICE, PPN, NAME.EXT

.DIR ALL:[]/SNAME/SNOPPN           ; by DEVICE, NAME.EXT

.DIR ALL:[]/SNAME/SNODEV/SNOPPN    ; by NAME.EXT

Note that except for these two sort modifiers, it only makes sense to specify one sort option. (Command switches are not ordered, so there is no way to distinguish, say, /SNAME/SUDATE from /SUDATE/SNAME). Also note that adding /SNODEV or /SNOPPN changes the output format slightly. Instead of providing subtotals when the DEV+PPN changes and showing the DEV:[P,PN] just for the first file of each new group, it lists the DEV:[P,PN] on every file.