Bitfields for AMD-645 Miscellaneous Control 3 register:
Bit(s)	Description	)
 7-4	reserved (0)
 3	disable RTC PORT 0074h and PORT 0075h
 2	disable integrated USB controller
 1	disable integrated IDE controller
 0	add 512K to offset 4Eh bits 15-12 at top of PCI memory
SeeAlso: #01011,#01018,#01019,PORT 0074h"AMD-645"