Format of parameter block for function 73h:
Offset	Size	Description	)
 00h	BYTE	???
		00h ATA card inserted ???
		80h ATA card not inserted ???
 01h	BYTE	length of parameter block ???
		apparently always 40h
 02h	BYTE	???
		00h ATA card not inserted ???
		0Dh ATA card inserted ???
 03h  2 BYTEs	??? (apparently always 00h)
 05h	BYTE	drive number (0=first) ???
 06h	BYTE	total number of drives ???
 07h	BYTE	???
		00h ATA card not inserted ???
		01h ATA card inserted ???
 08h 17 BYTEs	???
 19h	BYTE	???
		00h ATA card not inserted ???
		01h ATA card inserted ???
 1Ah	BYTE	??? (apparently always 01h)
 1Bh	BYTE	???
		00h ATA card not inserted ???
		01h ATA card inserted ???
 1Ch  2 BYTEs	??? (apparently always 0015h)
 1Eh  2 BYTEs	???
 20h  2 BYTEs	??? (apparently always 0110h)
 22h 15 BYTEs	???
 31h  2 BYTEs	??? (apparently always 7000h)
 33h 11 BYTEs	driver signature
		"AWARD PDISK" for Award PCDISK.EXE PCMCIA/ATA driver
		"MS-BIOS    " for HP 200LX generic ATA driver
 3Eh  2 BYTEs	???
Notes:	parameter structure possibly depends on driver
	this function is not supported by the SystemSoft ATADRV.EXE and the
	  Phoenix PCMATA.SYS PCMCIA/ATA drivers