307013-003 Datasheet, PDF (170/848 Pages) Intel Corporation – Intel I/O Controller Hub 7

Functional Description
Note:
During boot, THRMTRIP# is ignored until SLP_S3#, PWROK, VRMPWRGD/VGATE, and
PLTRST# are all ‘1’. During entry into a powered-down state (due to S3, S4, S5 entry,
power cycle reset, etc.) THRMTRIP# is ignored until either SLP_S3# = 0, or
PWROK = 0, or VRMPWRGD/VGATE = 0.
A thermal trip event will:
• Set the AFTERG3_EN bit
• Clear the PWRBTN_STS bit
• Clear all the GPE0_EN register bits
• Clear the SMB_WAK_STS bit only if SMB_SAK_STS was set due to SMBus slave
receiving message and not set due to SMBAlert
5.14.9.6
BM_BUSY# (Mobile/Ultra Mobile Only)
The BM_BUSY# signal is an input from a graphics component to indicate if it is busy. If
prior to going to the C3 state, the BM_BUSY# signal is active, then the BM_STS bit will
be set. If after going to the C3 state, the BM_BUSY# signal goes back active, the ICH7
will treat this as if one of the PCI REQ# signals went active. This is treated as a break
event.
5.14.10 ALT Access Mode
Before entering a low power state, several registers from powered down parts may
need to be saved. In the majority of cases, this is not an issue, as registers have read
and write paths. However, several of the ISA compatible registers are either read only
or write only. To get data out of
write-only registers, and to restore data into read-only registers, the ICH7 implements
an ALT access mode.
If the ALT access mode is entered and exited after reading the registers of the ICH7
timer (8254), the timer starts counting faster (13.5 ms). The following steps listed
below can cause problems:
1. BIOS enters ALT access mode for reading the ICH7 timer related registers.
2. BIOS exits ALT access mode.
3. BIOS continues through the execution of other needed steps and passes control to
the operating system.
After getting control in step #3, if the operating system does not reprogram the system
timer again, the timer ticks may be happening faster than expected. For example DOS
and its associated software assume that the system timer is running at 54.6 ms and as
a result the time-outs in the software may be happening faster than expected.
Operating systems (e.g., Microsoft Windows* 98, Windows* 2000, and Windows NT*)
reprogram the system timer and therefore do not encounter this problem.
For some other loss (e.g., Microsoft MS-DOS*) the BIOS should restore the timer back
to 54.6 ms before passing control to the operating system. If the BIOS is entering ALT
access mode before entering the suspend state it is not necessary to restore the timer
contents after the exit from ALT access mode.
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Intel ^® ICH7 Family Datasheet