Bitfields for OPTi 82C750 Vendetta (device 1) serial interrupt mode control:
Bit(s)	Description	)
 7-6	serial interrupt control mode
	00 = continuous
	01 = idle
	1x = active
 5	reserved
 4	data frame slot support
	0 = 17 slots (IRQ15-IRQ3, IRQ1-IRQ0, SMI#, IOCHK#)
	1 = 21 slots (IRQ15-IRQ3, IRQ1-IRQ0, SMI#, IOCHK#, PCIRQ3#-PCIRQ0#)
 3-2	CPU access PCI priority
	00 = lowest
	01 = higher after 4 PCI master grants
	10 = higher after 2 PCI master grants
	11 = higher after 3 PCI master grants
 1-0	serial interrupt start frame pulse width in continuous/active mode
	00 = 4/3 CLK
	01 = 6/5 CLK
	10 = 8/7 CLK
	11 = reserved
SeeAlso: #00939,#00952