INT 16 - PC-Cache v6+ - INSTALLATION CHECK                                      
	AX = FFA5h
	CX = 1111h
Return: CH = 00h if installed
	    ES:DI -> internal data (see #00620)
	    CL = cache state
		01h enabled
		02h disabled
SeeAlso: INT 13/AH=27h,INT 13/AH=A0h,INT 21/AH=2Bh/CX=4358h


Format of PC-Cache internal data:
Offset	Size	Description	(Table 00620)
-1Ch 20 BYTEs	cached drive list, one byte per drive A: to T:
		each byte is either blank (20h) or drive letter (41h-54h)
 -8	BYTE	???
 -7	WORD	number of physical transfers (scaled down to 0000h-7FFFh)
 -5	WORD	number of saved transfers (scaled down to 0000h-7FFFh)
 -3   3 BYTEs	???