Intel
82801BA ICH2 Datasheet
9-63
LPC Interface Bridge Registers (D31:F0)
9.8.3.5
PROC_CNT—Processor Control Register
I/O Address:
PMBASE + 10h
(
ACPI P_BLK)
00000000h
No (bits 7:5 are write once)
Core
Attribute:
Size:
Usage:
R/W
32-bit
ACPI or Legacy
Default Value:
Lockable:
Power Well:
Bit
Description
31:18
Reserved.
17
Throttle Status (THTL_STS)
—RO.
0 = No clock throttling is occurring (maximum processor performance).
1 = Indicates that the clock state machine is in some type of low power state (where the processor
is not running at its maximum performance): thermal throttling or hardware throttling.
16:9
Reserved
8
Force Thermal Throttling (FORCE_THTL)
—R/W. Software can set this bit to force the thermal
throttling function. This has the same effect as the THRM# signal being active for 2 seconds.
0 = No forced throttling.
1 = Throttling at the duty cycle specified in THRM_DTY starts immediately (no 2 second delay), and
no SMI# is generated.
7:5
Thermal Duty Cycle (THRM_DTY).
This write-once 3-bit field determines the duty cycle of the
throttling when the thermal override condition occurs. The duty cycle indicates the approximate
percentage of time the STPCLK# signal is asserted while in the throttle mode. The STPCLK# throttle
period is 1024 PCICLKs. Note that the throttling only occurs if the system is in the C0 state. If in the
C2 state, no throttling occurs.
There is no enable bit for thermal throttling, because it should not be disabled. Once the
THRM_DTY field is written, any subsequent writes will have no effect until PCIRST# goes active.
THRM_DTY
Throttle Mode
PCI Clocks
000
RESERVED (Default)
512
(Will be 50%)
001
87.5%
896
010
75.0%
768
011
62.5%
640
100
50%
512
101
37.5%
384
110
25%
256
111
12.5%
128
4
Throttling Enable (THT_EN):
When this bit is set and the system is in a C0 state, processor-
controlled STPCLK# throttling is enabled. The duty cycle is selected in the THTL_DTY field.
0 = Disable
1 = Enable
3:1
Throttling Duty Cycle (THTL_DTY):
This 3-bit field determines the duty cycle of the throttling when
the THTL_EN bit is set. The duty cycle indicates the approximate percentage of time the STPCLK#
signal is asserted (low) while in the throttle mode. The STPCLK# throttle period is 1024 PCICLKs.
THTL_DTY
Throttle Mode
PCI Clocks
000
RESERVED (Default)
512
(Will be 50%)
001
87.5%
896
010
75.0%
768
011
62.5%
640
100
50%
512
101
37.5%
384
110
25%
256
111
12.5%
128
0
Reserved
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