82801FB Datasheet, PDF (391/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

LPC Interface Bridge Registers (D31:F0)
10.7.2 NMI_EN—NMI Enable (and Real Time Clock Index)
Register (LPC I/F—D31:F0)
I/O Address:
70h
Default Value: 80h
Lockable:
No
Attribute:
Size:
Power Well:
R/W (special)
8-bit
Core
Note: The RTC Index field is write-only for normal operation. This field can only be read in Alt-Access
Mode. Note, however, that this register is aliased to Port 74h (documented in), and all bits are
readable at that address.
Bits
Description
NMI Enable (NMI_EN) — R/W (special).
7 _{0 = Enable NMI sources.}
1 = Disable All NMI sources.
6:0
Real Time Clock Index Address (RTC_INDX) — R/W (special). This data goes to the RTC to
select which register or CMOS RAM address is being accessed.
10.7.3
PORT92—Fast A20 and Init Register (LPC I/F—D31:F0)
I/O Address:
92h
Default Value: 00h
Lockable:
No
Attribute:
Size:
Power Well:
R/W
8-bit
Core
Bit
Description
7:2 Reserved
Alternate A20 Gate (ALT_A20_GATE) — R/W. This bit is Or’d with the A20GATE input signal to
generate A20M# to the processor.
1
0 = A20M# signal can potentially go active.
1 = This bit is set when INIT# goes active.
0
INIT_NOW — R/W. When this bit transitions from a 0 to a 1, the ICH6 will force INIT# active for 16
PCI clocks.
Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet
391