Format of SMARTDRV status record:
Offset	Size	Description	)
 00h	BYTE	write-through flag (always 01h)
 01h	BYTE	writes should be buffered (always 00h)
 02h	BYTE	cache enabled if 01h
 03h	BYTE	driver type (01h extended memory, 02h expanded)
 04h	WORD	clock ticks between cache flushes (currently unused)
 06h	BYTE	cache contains locked tracks if nonzero
 07h	BYTE	flush cache on INT 19 reboot if nonzero
 08h	BYTE	cache full track writes if nonzero
 09h	BYTE	double buffering (for VDS) state (00h off, 01h on, 02h dynamic)
 0Ah	DWORD	original INT 13 vector
 0Eh	BYTE	minor version number
 0Fh	BYTE	major version number
 10h	WORD	unused
 12h	WORD	sectors read			\
 14h	WORD	sectors already in cache	 > may be scaled rather than
 16h	WORD	sectors already in track buffer /  absolute counts
 18h	BYTE	cache hit rate in percent
 19h	BYTE	track buffer hit rate in percent
 1Ah	WORD	total tracks in cache
 1Ch	WORD	number of tracks in use
 1Eh	WORD	number of locked tracks
 20h	WORD	number of dirty tracks
 22h	WORD	current cache size in 16K pages
 24h	WORD	original (maximum) cache size in 16K pages
 26h	WORD	minimum cache size in 16K pages
 28h	DWORD	pointer to byte flag to increment for locking cache contents