INT 2F - SMARTDRV v4.00+ - STATUS
AX = 4A10h
BX = 0003h
BP = drive number (0=A, 1=B, etc.)
FFFFh = all drives (NWCACHE only)
DL = subfunction
00h only get information
01h turn on read cache
02h turn off read cache
03h turn on write cache
04h turn off write cache
05h reduce cache size
CX = number of KB to reduce (can't shrink below min size)
06h increase cache size
CX = number of KB to increase (can't grow above max size)
Return: AX = BABEh if OK
DL = status (see #02801)
DL = FFh if drive does not exist
Notes: If the read cache is off, reads will not be cached, but writes will
continue to be cached if the write-cache is enabled.
this function is also supported by PC-Cache v8.0.
SMARTDRV flushes the cache if sub-functions 02h or 04h have been
called to disable read or write caching.
On calling this function, NWCACHE flushes any delayed writes,
but you should not rely on this, since this behavior may vanish
in future versions.
BUG: The MS-DOS 6.20+ SCANDISK disables a SMARTDRV 4+ compatible cache
for the drive it is about to process. However, at least when the
cache loaded is NWCACHE, the cache will still remain disabled for
this drive after SCANDISK has finished. The reason for this behavior
is not yet known. The workaround is to re-enable with the
NWCACHE d:+ syntax afterwards, where d: is the corresponding