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Low Power Features
2.4
FSB Low Power Enhancements
The processor incorporates FSB low power enhancements:
• Dynamic FSB Power Down
• BPRI# control for address and control input buffers
• Dynamic Bus Parking
• Dynamic On-Die Termination disabling
• Low V
• Dynamic FSB frequency switching
The processor incorporates the DPWR# signal that controls the data bus input buffers
on the processor. The DPWR# signal disables the buffers when not used and activates
them only when data bus activity occurs, resulting in significant power savings with no
performance impact. BPRI# control also allows the processor address and control input
buffers to be turned off when the BPRI# signal is inactive. Dynamic Bus Parking allows
a reciprocal power reduction in GMCH address and control input buffers when the
processor deasserts its BR0# pin. The On-Die Termination on the processor FSB buffers
is disabled when the signals are driven low, resulting in additional power savings. The
low I/O termination voltage is on a dedicated voltage plane independent of the core
voltage, enabling low I/O switching power at all times.
2.5
Processor Power Status Indicator (PSI-2) Signal
The processor incorporates the PSI# signal that is asserted when the processor is in a
reduced power consumption state. PSI# can be used to improve intermediate and light
load efficiency of the voltage regulator, resulting in platform power savings and
extended battery life. The algorithm that the processor uses for determining when to
assert PSI# is different from the algorithm used in previous mobile processors. PSI-2
functionality is expanded further to support three processor states:
• Both cores are in idle state
• Only one core active state
• Both cores are in active state
PSI-2 functionality improves overall voltage regulator efficiency over a wide power
range based on the C-state and P-state of the two cores. The combined C-state and P-
state of both cores are used to dynamically predict processor power.
The real-time power prediction is compared against a set of predefined and configured
values of CHH and CHL. CHH is indicative of the active C-state of both the cores and
CHL is indicative that only one core is in active C-state and the other core is in low
power core state. PSI-2# output is asserted upon crossing these thresholds indicating
that the processor requires lower power. The voltage regulator will adapt its power
output accordingly. Additionally the voltage regulator may switch to a single phase and/
or asynchronous mode when the processor is idle and fused leakage limit is less than or
equal to the BIOS threshold value.
Datasheet
(I/O termination voltage)
CCP
§
19
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