As said in that page and the documentation, the read-ahead is the [,X] part, which is actually disabled by default in every DOS past 6.x (incl FreeDOS). The fir

As said in that page and the documentation, the read-ahead is the [,X] part, which is actually disabled by default in every DOS past 6.x (incl FreeDOS). The first part is the number of primary buffers which is indeed "for keeping recently read data in RAM". Smartdrv, like Fastopen, just allows disk buffers to survive a Close File call. Normally DOS only does close-to-open consistency i.e. buffers are flushed on close. Smartdrv specifically also allows write-back rather than write-through. And, anyway: yes, Smartdrv is enabled by default in 6.x installs with enough memory.