EP80579 Datasheet, PDF (1915/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
50.2.2.2
50.2.2.3
initiated passive cooling. Refer to Section 50.2.2.2, “Processor Passive Cooling” for
more information.
• By setting the PROCHOT_POL bit to high, another SMI# or SCI# can optionally be
generated when the PROCHOT# signal goes back high. This allows the software
(pre-boot firmware or ACPI) to turn off the cooling methods.
• PROCHOT# assertion does not cause a TCO event message in S3 or S4. The level of
the signal is not reported in the heartbeat message.
Processor Passive Cooling
The EP80579 provides a processor-initiated passive cooling feature that actives a clock
throttling mechanism, which can be used by power management software or pre-boot
firmware to reduce the temperature.
The FORCE_THTL bit allows the pre-boot firmware to force passive cooling independent
of the ACPI software (which uses the THTL_EN and THTL_DTY bits). The FORCE_THTL
bit has the following behavior:
• If the FORCE_THTL bit is set, the EP80579 will start throttling using the ratio in the
PROCHOT_DTY field. The duty cycle indicates the approximate percentage of time
the STPCLK# signal is asserted while in thermal throttle mode. The STPCLK#
throttle period is 1024 PCICLKs (PCICLK = 33 MHz). Throttling only occurs if the
system is in the C0 state. If in the C2, C3, or C4 state, no throttling occurs.
Note: Refer to Table 50-2 for duty cycle ratio settings.
• If the FORCE_THTL bit is turned off (cleared), the EP80579 will stop throttling,
unless the THTL_EN bit is set (indicating that ACPI software is attempting
throttling).
• If both the THTL_EN and FORCE_THTL bits are set, then the IICH uses the duty
cycle defined by the PROCHOT_DTY field, not the THTL_DTY field. (PROCHOT_DTY
has higher priority).
• Once the PROCHOT_DTY field is written, subsequent writes have no effect until
PLTRST# goes active.
On-Demand Passive Cooling
The EP80579 provides an on-demand passive cooling feature, which may be used in
customer designs that require power management capabilities that take advantage of
clock throttling. The on-demand feature is similar to the processor passive cooling in
that it supports clock throttling, but the on-demand feature is initiated by software
setting the THTL_EN and THTL_DTY bits.
The on-demand passive cooling feature behaves as follows:
• Software sets the THTL_DTY bits to select throttle ratio and the THTL_EN bit to
enable the throttling.
• Throttling results in STOPCLK# active for a minimum time of 12.5% and a
maximum of 87.5%. The period is 1024 PCI clocks (PCICLK = 33 MHz). Thus, the
STOPCLK# signal can be active for as little as 128 PCI clocks or as much as 896 PCI
clocks. The actual slowdown (and cooling) of the processor will depend on the
instruction stream, because the processor is allowed to finish the current
instruction. Furthermore, the EP80579 waits for the STOP-GRANT cycle before
starting the count for the time the STOPCLK# signal is active.
Note: Refer to Table 50-2 for duty cycle ratio settings.
August 2009
Order Number: 320066-003US
Intel^® EP80579 Integrated Processor Product Line Datasheet
1915