Bitfields for Intel 82371FB/82371SB/82371MX IDE timing modes:
Bit(s)	Description	)
 15	IDE decode enable
 14	(82371SB) slave IDE timing register enable (see #01224)
	(82371MX) primary/secondary address decode (=0 primary, =1 secondary)
 13-12	IORDY# sample point
	00 five clocks after DIOx# assertion
	01 four clocks
	10 three clocks
	11 two clocks
 11-10	reserved
 9-8	recovery time between IORDY# sample point and DIOx#
	00 four clocks
	01 three clocks
	10 two clocks
	11 one clock
 7	(FB/SB) DMA timing enable only, drive 1
	(MX) reserved
 6	prefetch and posting enable, drive 1
 5	IORDY# sample point enable drive select 1
 4	fast timing bank drive select 1
 3	(FB/SB) DMA timing enable only, drive 0
	(MX) reserved
 2	prefetch and posting enable, drive 0
 1	IORDY# sample point enable drive select 0
 0	fast timing bank drive select 0
SeeAlso: #01214,#01168