INT 2F - SMARTDRV v4.00+ - API
        AX = 4A10h
        BX = command
            0000h installation check and hit ratios
                Return: AX = BABEh if installed
                            DX:BX = cache hits
                            DI:SI = cache misses
                            CX = ???
                            BP = version (4.00 = 0400h)
            0001h reset cache
            0002h flush buffers
            0003h status
                BP = drive # (0=A, 1=B, etc.)
                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
                Return: AX = BABEh if OK
                        DL = status
                            bit 7  not cached
                            bit 6  write-through
                            bit 5  ???
                            bits 0-4 drive # (0=A, 1=B...)
                        DL = FFh if drive does not exist
                Note:   If the read cache is off, reads will not be cached,
                          but writes will continue to be cached if the write-
                          cache is enabled.
            0004h cache size
                Return: AX = ???
                        BX = largest number of elements
                        CX = size of elements in bytes
                        DX = number of elements under Windows
            0005h double-buffer status
                BP = drive # (0=A, 1=B...)
                Return: AX = BABEh if double-buffered
            0007h ???
                Return: DI = random number???
            000Ah get table pointer???
                Return: ES:BX -> table of about 10 bytes or 5 words. Seems to
                                be words pointing to memory addresses
                                containing info??? (see below)
            1234h signal serious error
                pops up a message box saying that a serious error occurred and
                  to hit R to retry.
SeeAlso: INT 21/AX=4403h"SMARTDRV"

Format of data table:
Offset  Size    Description
 00h  8 BYTEs   ???
 08h    WORD    offset of WORD containing number of elements in cache